CELL BIOLOGY AND PHYSIOLOGY
Prokaryotic and Eukaryotic Cells
a. Compare prokaryotic cells, eukaryotic cells, and viruses in terms of complexity, general structure, differentiation, and their requirements for growth and replication
Prokaryotes- cells that do not have an organized nucleus. Simplest and smallest type that can live independently. They are the evolutionary precursors to eukaryote cells. Very important fellows as they help recycle Earth's nutrients, decompose waste, and can even help to make the sun's energy available to all animal life!
General Characteristics of Prokaryotes:
Cell Wall: This tough wall made out of peptidoglycan is present in most prokaryotes. They get their tensile strength from murein. Muramic acid, one of the major molecules in murein, never occurs in the cell walls of the eukaryotic cells. Penicillin is effective because it inhibits the synthesis of murein and, as a result, the production of bacteria. Penicillin does not act against eukaryotic cells.
Cell membrane: this is very much like eukaryotic cells, except that prokaryotic cell membrane lacks cholesterol and other steroids. In the archaeobacteria, the cell membrane is composed of modified branched fatty acids. In the Eubacteria, the membrane is composed of straight-chain fatty acids. The surface area in some prokaryotes are increased by convolutions (folds and loops). This convoluted cell membrane has incorporated in their structure the electron transport systems and enzymes, which are necessary for the chemical events taking place during respiration.
Cytoplasm: highly granulated due to the large presence of the ribosomes (the only cellular organelles found in most prokaryotes). Ribosomes function the same as they do in the eukaryotic cells by being the sites of protein synthesis.
DNA: Unlike eukaryotes which stores its DNA in the nucleus of cells, prokaryote cells have no membrane-bound organelles. Instead, prokaryotic cells contain a circular molecule of DNA that is not enclosed by a membrane.
Reproduction: The DNA is replicated first. Then the cell wall and the plasma membrane grow inward, ultimately dividing the cell into two. This cell division is called binary fission. They can also reproduce asexually by conjugation, transduction, and transformation.
Locomotion- there are a few prokaryotes that have a flagella that allows them to swim and move. These tails are connected to the cell using several interlocking proteins. The flagella of prokaryotes and eukaryotes have different proteins and internal structure. Both have the same function. The ability to swim is called cell motility and this ability represents a big step in evolution. A motile organism is able to hunt for food, seek mates, avoid danger, etc.
A group of prokaryotes known as the archaea can be found in very harsh environments, such as salt lakes, in digestive tract of animals and insects, hot sulfur springs, and hydrothermal vents. Archaea looks like bacteria but there are some distinct differences, and similarities, between the two. They both measure around 1-3 micrometers in diameter if they are round and 2-4 micrometers in length for the rod-shaped. While they both can be round or rod shaped, bacteria can come in a few other shapes such as corkscrew (spirila), flexible spirals (spirochetes), curves (vibrios), and others are shapeless and do not possess a constant shape; both are able to live in aerobic or anaerobic environments; their cells walls are supported differently in that the bacteria is supported by the polymer peptidoglycan and the Archaea is pseudomurein; the bacteria's membranes consists of fatty acids of straight-chain and the archeae's membrane consists of massive branched-chain fatty acids; unlike bacteria, archaeas are able to produce methane gas from carbon dioxide; unlike archaeas, bacteria is able to convert the sun's energy to chemical energy through photosynthesis; unlike archaeas, some bacteria can cause diseases in plants and animals.
These simple organisms are able to so much! Here is a short lists of the tasks they are able to carry out: recycle carbon, nitrogen, sulfur, phosphorus, and metals; perform photosynthesis; decompose dead organic matter; produce greenhouse gases; cause diseases in plants, animals, and insects; protect the body from infection and even strengthen the immune system; digest fibers in animal diets.
Eukaryotes- Which organisms are composed of eukaryotic cells? Think of a bacteria and archaea. Got that in your mind? Okay, now wipe them from your thoughts. Everything else is a eukaryote. Eukaryotes are more complex than prokaryotes. Both plants and animals consist of eukaryotic cells. The first eukaryotes appeared about 3.5 billion years ago. Over the next 2.5 billion years, the cells became more sturdy. The first eukaryotes likely evolved from prokaryotes that caught and digested other prokaryotes. The idea is that most of the time, a predator cell would digest the smaller cell. Sometimes, however, a few pieces of the ingested cell remained intact inside of the predator. A few of these pieces would serve a purpose and, over time, the predator cells that had ingested other prokaryotes would become more complicated due to those pieces and eventually a new type of cell developed. This new cell contained internal structures that carried out specific functions. And, the organelle of eukaryote cells evolved.
General Characteristics of a Eukaryote:
Cell Wall: There are two types, the Gram positive cell wall and the Gram negative cell wall. In 1884, a Danish Microbiologist named Hans Christian Gram developed a technique for straining bacteria. This technique became useful in distinguishing groups of organisms, particular among the Eubacteria. The idea behind gram staining is based on the cells ability to absorb certain dyes. Bacterial cell walls that are made up of peptidoglycans (amino sugars) absorb purple dye and washing those cells with alcohol does not remove the dye. These purple-staining cells are called Gram positive. On the other hand, cell walls composed of lipopolysaccharides do not hold on to the purple dye and can easily be bleached with alcohol are called Gram negative. These cells stain red with dyes such as safranin. Gram positive have a thick layer of peptidoglycan, which absorbs the gram stain. Gram negative have a thick lipid bilayer on the outside, which is selectively permeable- not everything can pass through it, one of those is the gram stain. The composition of the cell wall Gram positive versus Gram negative, can tell us about the behavior of the cell. The Gram positive bacteria are more susceptible to antibiotics than gram-negative bacteria since things can pass through its cell walls more easily.
Nucleus: contains one or more non-membrane bound areas called nucleoli where the cell manufactures ribosomes
Ribosomes: these are small units found scattered in the cytoplasm that act as a site of protein synthesis
Mitochondrion: this is the site of respiration and energy generation
Golgi apparatus: this makes various cellular products, sort them, packages them
Endoplasmic reticulum: site of membrane synthesis. Rough ER holds ribosomes, smooth ER lacks ribosomes.
Lysosome: digests food, only exists in animal cells
Centrosome: produces slender tubules that guide the process of cell division
Perioxisome: produces hydrogen peroxide from excess oxygen molecules and degrades the hydrogen peroxide to protect the cell from damage
Chloroplast: site of photosynthesis, only found in plant cells
Vacuole: sac that stores excess food, digests some foods, and breaks down waste
Except for the ribosomes, the rest of the organelles in the list makes eukaryotes different from prokaryotes.
Protists- these are single-celled eukaryotes. Very diverse in cell shape, flexibility, different methods of swimming, methods for finding and ingesting food, and reproduction. Similar to prokaryotes because they make their way through life on their own. Finding their own food, sense and react to danger, reproduce without the need for another cell. Like eukaryotes in that they have more complex structures and often more complex life cycles. Examples of protists includes the amoeba, diplomonads, algae, oomycetes, and ciliates.
Virus- these little, parasitic buggers exist in this gray area between the living and the nonliving. They resemble living things as they are small nucleic acid units, either RNA or DNA, that is surrounded by a protective protein coat (capsid). They can also replicate- an ability that living things can perform, not the non-living. However, they do not take in nutrients, grow, reproduce on their own, maintain homeostasis, or sense and respond to their environment around them. Their "life cycle" is an interesting story... Viruses are also known as phage and they can only survive by infecting a live cell and turning this cell into a factory to manufacture more viruses. They reproduce by making the cell do all of the work. What nerve!
Viruses slip their DNA or RNA across the plasma membrane and enters the nucleus. It infiltrates the cell's DNA. There are two known methods for how viruses reproduce and spread after this infiltration occurs:
Lytic cycle: In this cycle, the phage ends up destroying the host cell. As these copied nucleic acids organize as phages and the number of phages become too large for the host cell to hold, the cell membrane breaks and releases the phage to infect the neighboring cells. And the cycle continues.
Lysogenic cycle: in this method, the virus does not kill the host cell. When the virus inserts its DNA or RNA into the host cell, it gets incorporated into the cells chromosome. The viral DNA/RNA is replicated along with the chromosomal material. Lysogney can continue for many cycles. All the while the cell continues to manufacture and ship new batches of virus with an intent to spread infection. At some point in lysogeny, under certain conditions, the virus switches over to the lytic cycle.
Here is a video below illustrating these two processes
Prokaryotes- cells that do not have an organized nucleus. Simplest and smallest type that can live independently. They are the evolutionary precursors to eukaryote cells. Very important fellows as they help recycle Earth's nutrients, decompose waste, and can even help to make the sun's energy available to all animal life!
General Characteristics of Prokaryotes:
Cell Wall: This tough wall made out of peptidoglycan is present in most prokaryotes. They get their tensile strength from murein. Muramic acid, one of the major molecules in murein, never occurs in the cell walls of the eukaryotic cells. Penicillin is effective because it inhibits the synthesis of murein and, as a result, the production of bacteria. Penicillin does not act against eukaryotic cells.
Cell membrane: this is very much like eukaryotic cells, except that prokaryotic cell membrane lacks cholesterol and other steroids. In the archaeobacteria, the cell membrane is composed of modified branched fatty acids. In the Eubacteria, the membrane is composed of straight-chain fatty acids. The surface area in some prokaryotes are increased by convolutions (folds and loops). This convoluted cell membrane has incorporated in their structure the electron transport systems and enzymes, which are necessary for the chemical events taking place during respiration.
Cytoplasm: highly granulated due to the large presence of the ribosomes (the only cellular organelles found in most prokaryotes). Ribosomes function the same as they do in the eukaryotic cells by being the sites of protein synthesis.
DNA: Unlike eukaryotes which stores its DNA in the nucleus of cells, prokaryote cells have no membrane-bound organelles. Instead, prokaryotic cells contain a circular molecule of DNA that is not enclosed by a membrane.
Reproduction: The DNA is replicated first. Then the cell wall and the plasma membrane grow inward, ultimately dividing the cell into two. This cell division is called binary fission. They can also reproduce asexually by conjugation, transduction, and transformation.
Locomotion- there are a few prokaryotes that have a flagella that allows them to swim and move. These tails are connected to the cell using several interlocking proteins. The flagella of prokaryotes and eukaryotes have different proteins and internal structure. Both have the same function. The ability to swim is called cell motility and this ability represents a big step in evolution. A motile organism is able to hunt for food, seek mates, avoid danger, etc.
A group of prokaryotes known as the archaea can be found in very harsh environments, such as salt lakes, in digestive tract of animals and insects, hot sulfur springs, and hydrothermal vents. Archaea looks like bacteria but there are some distinct differences, and similarities, between the two. They both measure around 1-3 micrometers in diameter if they are round and 2-4 micrometers in length for the rod-shaped. While they both can be round or rod shaped, bacteria can come in a few other shapes such as corkscrew (spirila), flexible spirals (spirochetes), curves (vibrios), and others are shapeless and do not possess a constant shape; both are able to live in aerobic or anaerobic environments; their cells walls are supported differently in that the bacteria is supported by the polymer peptidoglycan and the Archaea is pseudomurein; the bacteria's membranes consists of fatty acids of straight-chain and the archeae's membrane consists of massive branched-chain fatty acids; unlike bacteria, archaeas are able to produce methane gas from carbon dioxide; unlike archaeas, bacteria is able to convert the sun's energy to chemical energy through photosynthesis; unlike archaeas, some bacteria can cause diseases in plants and animals.
These simple organisms are able to so much! Here is a short lists of the tasks they are able to carry out: recycle carbon, nitrogen, sulfur, phosphorus, and metals; perform photosynthesis; decompose dead organic matter; produce greenhouse gases; cause diseases in plants, animals, and insects; protect the body from infection and even strengthen the immune system; digest fibers in animal diets.
Eukaryotes- Which organisms are composed of eukaryotic cells? Think of a bacteria and archaea. Got that in your mind? Okay, now wipe them from your thoughts. Everything else is a eukaryote. Eukaryotes are more complex than prokaryotes. Both plants and animals consist of eukaryotic cells. The first eukaryotes appeared about 3.5 billion years ago. Over the next 2.5 billion years, the cells became more sturdy. The first eukaryotes likely evolved from prokaryotes that caught and digested other prokaryotes. The idea is that most of the time, a predator cell would digest the smaller cell. Sometimes, however, a few pieces of the ingested cell remained intact inside of the predator. A few of these pieces would serve a purpose and, over time, the predator cells that had ingested other prokaryotes would become more complicated due to those pieces and eventually a new type of cell developed. This new cell contained internal structures that carried out specific functions. And, the organelle of eukaryote cells evolved.
General Characteristics of a Eukaryote:
Cell Wall: There are two types, the Gram positive cell wall and the Gram negative cell wall. In 1884, a Danish Microbiologist named Hans Christian Gram developed a technique for straining bacteria. This technique became useful in distinguishing groups of organisms, particular among the Eubacteria. The idea behind gram staining is based on the cells ability to absorb certain dyes. Bacterial cell walls that are made up of peptidoglycans (amino sugars) absorb purple dye and washing those cells with alcohol does not remove the dye. These purple-staining cells are called Gram positive. On the other hand, cell walls composed of lipopolysaccharides do not hold on to the purple dye and can easily be bleached with alcohol are called Gram negative. These cells stain red with dyes such as safranin. Gram positive have a thick layer of peptidoglycan, which absorbs the gram stain. Gram negative have a thick lipid bilayer on the outside, which is selectively permeable- not everything can pass through it, one of those is the gram stain. The composition of the cell wall Gram positive versus Gram negative, can tell us about the behavior of the cell. The Gram positive bacteria are more susceptible to antibiotics than gram-negative bacteria since things can pass through its cell walls more easily.
Nucleus: contains one or more non-membrane bound areas called nucleoli where the cell manufactures ribosomes
Ribosomes: these are small units found scattered in the cytoplasm that act as a site of protein synthesis
Mitochondrion: this is the site of respiration and energy generation
Golgi apparatus: this makes various cellular products, sort them, packages them
Endoplasmic reticulum: site of membrane synthesis. Rough ER holds ribosomes, smooth ER lacks ribosomes.
Lysosome: digests food, only exists in animal cells
Centrosome: produces slender tubules that guide the process of cell division
Perioxisome: produces hydrogen peroxide from excess oxygen molecules and degrades the hydrogen peroxide to protect the cell from damage
Chloroplast: site of photosynthesis, only found in plant cells
Vacuole: sac that stores excess food, digests some foods, and breaks down waste
Except for the ribosomes, the rest of the organelles in the list makes eukaryotes different from prokaryotes.
Protists- these are single-celled eukaryotes. Very diverse in cell shape, flexibility, different methods of swimming, methods for finding and ingesting food, and reproduction. Similar to prokaryotes because they make their way through life on their own. Finding their own food, sense and react to danger, reproduce without the need for another cell. Like eukaryotes in that they have more complex structures and often more complex life cycles. Examples of protists includes the amoeba, diplomonads, algae, oomycetes, and ciliates.
Virus- these little, parasitic buggers exist in this gray area between the living and the nonliving. They resemble living things as they are small nucleic acid units, either RNA or DNA, that is surrounded by a protective protein coat (capsid). They can also replicate- an ability that living things can perform, not the non-living. However, they do not take in nutrients, grow, reproduce on their own, maintain homeostasis, or sense and respond to their environment around them. Their "life cycle" is an interesting story... Viruses are also known as phage and they can only survive by infecting a live cell and turning this cell into a factory to manufacture more viruses. They reproduce by making the cell do all of the work. What nerve!
Viruses slip their DNA or RNA across the plasma membrane and enters the nucleus. It infiltrates the cell's DNA. There are two known methods for how viruses reproduce and spread after this infiltration occurs:
Lytic cycle: In this cycle, the phage ends up destroying the host cell. As these copied nucleic acids organize as phages and the number of phages become too large for the host cell to hold, the cell membrane breaks and releases the phage to infect the neighboring cells. And the cycle continues.
Lysogenic cycle: in this method, the virus does not kill the host cell. When the virus inserts its DNA or RNA into the host cell, it gets incorporated into the cells chromosome. The viral DNA/RNA is replicated along with the chromosomal material. Lysogney can continue for many cycles. All the while the cell continues to manufacture and ship new batches of virus with an intent to spread infection. At some point in lysogeny, under certain conditions, the virus switches over to the lytic cycle.
Here is a video below illustrating these two processes
Cellular Reproduction
a. Describe the stages of the cell cycle
In biology, the two types of cell division are asexual and sexual.
Cell Cycle in Prokaryotes: in these types of cells, their mode of reproduction is asexual known as binary fission. In binary fission, the cell splits into two nearly identical daughter cells. Done. Easy. Simple. Microbes can divide easily because they have only one chromosome. The task of splitting a cell requires little work when you compare it to the work that eukaryotes have to go through. The only thing that must be done is that after it replicates its DNA, that it separates the copies to each side of the cell so that the cell can divide down the middle, each side having a chromosome copy.
Asesxual reproduction is done without the union of gametes (sperm and egg).
4 types of asexual reproduction:
1) Budding: this is when an offspring begins as buds of the parent. When they mature, they drop off and mature.
2) Fragmentation: when a piece of an organism is cut off or breaks off from the main body. This piece grows and matures.
3) Binary Fission: as described above, this is when the organisms dives into two. Combination of mitosis and cytokinesis.
4) Parthenogenesis: deposition of unfertilized eggs which grow into adults
Cell Cycle in Eukaryotes:
As mentioned, the process of cell division demands more work from eukaryotes than in prokaryotes. Each eukaryotic cell has a repeating set of events that make up the life of every cell. While they can vary in length depending on the cell's function, the cell cycle can be described in a 5-step process.
A typical cell cycle have distinct phases:
G1 Phase: this is when the cell is growing and maturing. This is a long rest or interphase.
S Phase: this is a period of active syntheses of DNA
G2 Phase: this stage is when the cell prepares for division. This is another long period of mainly rest.
M Phase: This is the time when mitosis occurs.
The M phase takes up more than 10 person of the entire cell cycle. The G phases take up more than 50 percent. The S phase takes up about 25 percent.
Cells contain specific molecules that are devoted to triggering and stopping the steps in the cell cycle. The controls on a cell cycle come from two sources:
1) internal controls: mainly genes that have specifically evolved to control the cycle as well as sensors of the cell that tells it to slow down or speed up
2) external controls: these are factors in the environment that when detected by a cell induce faster or slower cycle
All cells also has a checkpoint that tells the cycle to either go or stop. These checkpoints help to prevent exhaustion of the cell's food supply, water, etc. Most cells have three main checkpoints (common in almost all cells are around in the middle of the G1 phase, end of the G2 phase, and halfway through the M phase) and a few minor checkpoints. If a cell does not receive a signal from either internal or external controls, then it will not divide or prepare for division. This time period is sometimes called the G0 phase.
b. Diagram and describe the stages of the mitotic process
Mitosis- This is the process of cell division when a plant or animal cell divides for growth or repair. Mitosis ensures that the two new nuclei (daughter cells) have the same number or chromosomes called diploid number. Mitosis always has four stages and before mitosis begins, there is always an interphase.
Interphase- This is an active period between cell division. The cell is preparing materials to produce “copies” of all of it components. Chromatin threads in nucleus duplicates. This is also during the time that the cell is growing and carrying out processes needed for life.
In biology, the two types of cell division are asexual and sexual.
Cell Cycle in Prokaryotes: in these types of cells, their mode of reproduction is asexual known as binary fission. In binary fission, the cell splits into two nearly identical daughter cells. Done. Easy. Simple. Microbes can divide easily because they have only one chromosome. The task of splitting a cell requires little work when you compare it to the work that eukaryotes have to go through. The only thing that must be done is that after it replicates its DNA, that it separates the copies to each side of the cell so that the cell can divide down the middle, each side having a chromosome copy.
Asesxual reproduction is done without the union of gametes (sperm and egg).
4 types of asexual reproduction:
1) Budding: this is when an offspring begins as buds of the parent. When they mature, they drop off and mature.
2) Fragmentation: when a piece of an organism is cut off or breaks off from the main body. This piece grows and matures.
3) Binary Fission: as described above, this is when the organisms dives into two. Combination of mitosis and cytokinesis.
4) Parthenogenesis: deposition of unfertilized eggs which grow into adults
Cell Cycle in Eukaryotes:
As mentioned, the process of cell division demands more work from eukaryotes than in prokaryotes. Each eukaryotic cell has a repeating set of events that make up the life of every cell. While they can vary in length depending on the cell's function, the cell cycle can be described in a 5-step process.
A typical cell cycle have distinct phases:
G1 Phase: this is when the cell is growing and maturing. This is a long rest or interphase.
S Phase: this is a period of active syntheses of DNA
G2 Phase: this stage is when the cell prepares for division. This is another long period of mainly rest.
M Phase: This is the time when mitosis occurs.
The M phase takes up more than 10 person of the entire cell cycle. The G phases take up more than 50 percent. The S phase takes up about 25 percent.
Cells contain specific molecules that are devoted to triggering and stopping the steps in the cell cycle. The controls on a cell cycle come from two sources:
1) internal controls: mainly genes that have specifically evolved to control the cycle as well as sensors of the cell that tells it to slow down or speed up
2) external controls: these are factors in the environment that when detected by a cell induce faster or slower cycle
All cells also has a checkpoint that tells the cycle to either go or stop. These checkpoints help to prevent exhaustion of the cell's food supply, water, etc. Most cells have three main checkpoints (common in almost all cells are around in the middle of the G1 phase, end of the G2 phase, and halfway through the M phase) and a few minor checkpoints. If a cell does not receive a signal from either internal or external controls, then it will not divide or prepare for division. This time period is sometimes called the G0 phase.
b. Diagram and describe the stages of the mitotic process
Mitosis- This is the process of cell division when a plant or animal cell divides for growth or repair. Mitosis ensures that the two new nuclei (daughter cells) have the same number or chromosomes called diploid number. Mitosis always has four stages and before mitosis begins, there is always an interphase.
Interphase- This is an active period between cell division. The cell is preparing materials to produce “copies” of all of it components. Chromatin threads in nucleus duplicates. This is also during the time that the cell is growing and carrying out processes needed for life.
Stage 1: Prophase- The nucleoli disappears. Chromatin (combination of DNA and proteins) thread coils up to form chromosomes.
Prometaphase- the nucleus' membrane disintegrates. The chromosomes attach to a system of microtubles that extend from one side of the cell to the other.
Prometaphase- the nucleus' membrane disintegrates. The chromosomes attach to a system of microtubles that extend from one side of the cell to the other.
Stage 2: Metaphase- The centrioles project protein fibers called spindle fibers which join together to form a sphere. Chromosomes move toward the equator and there centromeres becomes attached to spindle fibers.
In animals, this phase is the lognest phase in mitosis. This phase can last for 20 minutes.
Stage 3: Anaphase- Centromere duplicate and the two daughter chromosomes move to opposite poles of the spindle.
In animals, this phase is the shortest, only taking a few minutes.
Stage 4: Telephase- Spindle fibers and astral rays disappear and nuclear membrane forms around the daughter chromosomes. The centrioles also duplicate. Cytokinesis takes place (this is the division of of the cytoplasm). The cell cleaves in two and forms two daughter cells, each with a single set of chromosomes. The chromosomes become less dense and the DNA becomes less organized.
Plant and Animal Cell Anatomy and Physiology
a. Diagram the structure of the cell membrane and relate the structure to its function
The cell membrane is the outer boundary of a cell. Also known as plasma membrane. It has a intricate molecular structure. They are composed of proteins and fatty substances called lipids. Membranes serve an important role in that they choose what substances get into the cell and which substances exit the cell. This is called selective permeability.
Pores in the cell membrane are lined with small protein molecules. The proteins and lipids are aligned in a way to protect the cell's contents and also gives the cell the ability to choose materials it allows in and out. From the outside to the inside, the composition is comprised on a hydrophilic lipid (water-attracting), hydrophobic lipid (water-repelling), and a hydrophilic lipid. The interior membrane and the outside of the membrane are incompatible with water soluble compounds. So, the question is, if many of the nutrients a cell needs are water soluble, how do they get across the membrane? The transport of materials across the cell boundary is controlled by the globular proteins, the phospholipids, and the pores of the membrane, and the electrochemical nature of protoplasm.
Plant cells and prokaryotes have an exterior cell wall that lies on top of the membrane.
b. Explain methods of transport across the membrane (e.g., diffusion, active transport, endocytosis and exocytosis)
Fluid Mosaic Model: this model is used by biologist to explain how some molecules move into and out of cells while others cannot. The core of the membrane is made of compounds called phospholipids. The head of the phospholipid contains a phosphate group, the tails are fatty acids, and a variable organic group is attached to the phosphate head. The phosphate head is water-loving, but the lipid tails reject water. The fatty acid tails prevent soluble molecules from crossing the membrane. As mentioned above, water-soluble materials are able to enter the cell by way of the large, circular proteins that are set in the membrane. The large globular proteins are free to pass back and forth in the membrane and act as carrier molecules, carrying certain substances across the cell membrane. The scattered proteins form a pattern, or a mosaic.
Passive Transport: does not require the cell's chemical energy to move the molecules. Instead it depends on heat energy within the cell to increase the frequency with which molecules move.
Active Transport: this requires the use of chemical energy that is stored in ATP molecules in the cell. Types:
Exocytosis: this is when molecules are forced out of cells. Carried to the cell's surface by vacuoles or vesicles.
c. Explain the role of semipermeable membranes in cellular communication
A healthy membrane is selectively permeable because it allows substances needed for cell prosperity to enter and works to prohibit the penetration of unwanted and unfriendly substances. Sadly, this system is not always fool-proof and sometimes unwanted substances do pass through the membrane.
By using electron microscope images, it was observed that the embedded molecules can move sideways throughout the membrane, which is a fluid, not a solid. The membrane also has glycoproteins attached to the surface. The glycoprotein is a molecule that is used as an identification for proteins seeking a particular site for bonding. Each cell has a particular glycoprotein structure based on its need to attract or repel membrane traffic.
The proteins in the cell membrane are involved in a cellular communication. They receive chemical messages from other cells which is called signaling molecules. When these molecules bind with the proteins, they trigger a change in the protein. This causes a message to be sent into the cell and activate a specific cellular response.
The proteins embedded in the membrane serve many functions such as holding the membrane in a regular structure for easy bonding. They also function as receptor sites. In some cases the receptor protein is also a signal transducer that begins a series of enzyme-catalyzed reactions to stimulate a particular reaction within the cell. Transport proteins help substances move across the membrane. Many cell membrane proteins are multi-taskers as there are so many functions to perform. Sounds like my job as a teacher!
d. Explain the role of the endoplasmic reticulum and Golgi apparatus in the secretion of proteins
Discovered by the Italian biologist Camillio Golgi in 1898.
If a protein, or other substances, needs to be shipped outside the cell, transport vesicles travel to the Golgi apparatus. This organelle is responsible for packing up this shipment. The Golgi apparatus consists of flattened membrane-enclosed sacs. When it receives vesicles and their fluids from membranes of the endoplasmic reticulum, it will rewrap these vesicles in membranes by the Golgi body to form a shipping vesicle. It will also chemically mark them for destination points. It moves to the outer plasma membrane and fuses with it. The cellular products inside the vesicle either joins the membrane or continues to the cell's exterior. When they are shipped out of the cell, the products are referred to as secretions. Plants have several hundred Golgi bodies, animal cells usually around 10 to 20.
e. Explain the role of chloroplasts in obtaining and storing usable energy
Chloroplasts belongs to a group of structures which have the general name plastids. Plastids are membrane-bound and are found only in plants. Typically, they are free floating in the cytoplasm and hold pigment molecules or starch. Chloroplasts contain the green pigment chlorophyll. This is a special molecule that has the ability to trap light and convert it to a form of energy that plants can use to carry out the chemical steps in making food. This process is known as photosynthesis.
Chloroplasts are surrounded by a double membrane. Inside are flattened sacs called thylakoids. The thylakoids contain chlorophyll and it is here where photosynthesis takes place. Stroma is also found in the thylakoid sacs and is the dense ground substance that cushions the thylakoids.
Photosynthesis: the raw materials for photosynthesis are carbon dioxide and water. On the membrane of the thylakoids, chlorophyl and the accessory pigments are organized into functional groups called photosystems. Each of these photosystems has a reaction center or a light trap where special chlorophyl a molecule traps light energy. Two photosystems are used: Light Reaction and Dark Reaction (aka Calvin Cycle). Carbon dioxide enters and oxygen exits from the plan through adjustable openings on the underside of leaves called the stomata. Photosynthesis is an oxidation-reduction (redox) type of reaction. Reduction is the addition of an electron to an acceptor molecule. Oxidization is the removal of an electron from a molecule. Reduction stores energy in a compound and oxidation releases energy. When one substance is reduce, another is oxidized.
Photosyntheses can be described in two stages (as mentioned above), the light reaction and the dark reaction.
Light Reaction: occurs in the thylakoid's membrane. Light strikes the pigment and is captured. This light energy is absorbed by the chlorophyl molecules and transferred to make high-energy electrons. A pigment-protein complex captures the energy from the excited electrons and absorbs a water molecule. This water molecule splits apart to produce hydrogen, which is used from the energy-generating steps. Oxygen is released. The pigment, cytochrome, transfers the electrons to a second photosystem while pumping protons across the thylakoid membrane. The resulting proton gradient drives the formation of ATP. The electrons move to the dark reactions, where they are used to produce glucose.
Dark Reaction: as you may have guessed, this takes place even if no light is present. Uses energy from the light reaction to make sugar molecules. These fuel every other reaction in the cell. The cell consumes carbon dioxide and builds these to make glucose.
Animal cells do not have chloroplasts as these organisms do not make their own flood.
f. Explain the role of mitochondria in cellular respiration
As a runner, I have come to appreciate and respect the very important organelle, the mitochondrion! The mitochondrion is surrounded by a double membrane. It has a membrane of many folds fitted into its internal structure. These folds are covered with enzymes that are necessary for chemical reactions that release energy. The internal membranes is called the cristae and it forms compartments that provide additional work and storage areas for the complex task of cellular respiration. Each membrane consists of layers of protein and lipid molecules. The respiratory chain system is associated with the protein layer while the process of oxidative phophorylation involves the lipid layers.
Cellular respiration is a pathway of decomposition where it is a series of reactions that break down sugars, releasing energy along the way.
The oxygen system cannot be used directly as a source of energy but it does produce ATP in large quantities from sources in the body. Through a complex series of reactions metabolic by-products of carbohydrate, fat, or protein combine with oxygen to produce energy, carbon dioxide, and water.
Energy respiration is produced during two major phases:
anaerobic respiration: this process takes place in the cytoplasm and begins with the glucose molecule. With the assistance of enzymes, glucose is converted through a series of steps to form pyruvic acid. Throughout these steps either a hydrogen atom is given up or a water molecule is formed. When a hydrogen bond is broken, energy within that molecule becomes a bit more concentrated and is ultimately released to ADP molecules and stored between phosphate bonds. Whenever ADP accepts energy, inorganic phosphate is attached to the ADP forming ATP. There is a net gain of 2 ATPs.
aerobic respiration: this phase of cellular respiration takes place in mitochondria. The whole series of events of oxidate energy production primarily involves aerobic processing of carbohydrates and fats through the Kreb cycle and the electron transfer system. The process begins with pyruvic acid which is converted into acetyl coenzyme A. Fuel molecules are broken apart through chemical changes which releases a great deal of energy that has been stored in ATP molecules. The hydrogen atoms that were formed during glycolysis and aerobic respiration then enters the oxidate phosphorylation stage. These hydrogen atoms are passed along the electron transport chain which is found in the mitochondria's membrane. The hydrogen protons are pushed to the outside of the membrane which establishes an electrochemical gradient across the membrane. Energy resulting from the difference in potional across the membrane is used to form ATP. At the end of the electron transfer
So, the more mitochondria that an athlete possess, the better his or her endurance performance! Since running is an aerobic activity, the mitochondria is our aerobic engines that power this activity.
g. Explain the role of enzymes in chemical reactions and describe an experiment to test the catalytic role of enzymes and factors that affect enzyme activity (e.g., levels of protein organization, temperature, ionic conditions, concentration of enzyme and substrate, pH)
I love how one of my biology professors once described enzymes as a catalyst. I'm going to paraphrase her embellished story here but she said, "As a mom, I am trying to get my son out the door in the morning to catch the school bus. As I open the door, I use my foot to nudge him to hurry out the door. My foot doesn't fuse with my son or was consumed in the process. I kept my foot intact, but it did speed up the process of getting him out to the school bus." Okay, so obviously, she didn't physically use her foot to push her son out of the house so that he can catch the bus, but this little humorous imagery did help to firmly implant in my mind the role of enzymes as a catalyst.
Enzymes function as a catalyst to increase the rate of virtually all chemical reaction that take place in a living organism. Enzymes are not consumed and are constantly reused to catalyze the same specific reaction. Most enzymes are proteins and function is specific to their structure.
Enzymes depend on the correct structural alignment and orientation at the active site of the protein and the appropriate site of the reactants, called substrate, before the reaction can proceed. This geometric interaction is referred to as the lock-and-key model (first suggested by Emil Fischer in 1894). If a key and lock do not match, an action will not work- you cannot open the lock. So, the active site for the enzyme and the appropriately match site of the substrate must physically join before a reaction can occur, which is why the structure of the enzyme is important. The correct alignment and orientation must occur in order to connect the molecules.
Once the products in the reaction are formed, the enzyme is released to catalyze the same reaction for another substrate of the same type of molecule.
Denature of the enzyme may occur if it is heated which causes a change in shape, preventing it from performing its function.
h. Explain anabolic and catabolic pathways involved in the metabolism of macromolecules (e.g., polysaccharides, nucleic acids, proteins, lipids)
Metabolism involves two fundamental process:
The cell membrane is the outer boundary of a cell. Also known as plasma membrane. It has a intricate molecular structure. They are composed of proteins and fatty substances called lipids. Membranes serve an important role in that they choose what substances get into the cell and which substances exit the cell. This is called selective permeability.
Pores in the cell membrane are lined with small protein molecules. The proteins and lipids are aligned in a way to protect the cell's contents and also gives the cell the ability to choose materials it allows in and out. From the outside to the inside, the composition is comprised on a hydrophilic lipid (water-attracting), hydrophobic lipid (water-repelling), and a hydrophilic lipid. The interior membrane and the outside of the membrane are incompatible with water soluble compounds. So, the question is, if many of the nutrients a cell needs are water soluble, how do they get across the membrane? The transport of materials across the cell boundary is controlled by the globular proteins, the phospholipids, and the pores of the membrane, and the electrochemical nature of protoplasm.
Plant cells and prokaryotes have an exterior cell wall that lies on top of the membrane.
b. Explain methods of transport across the membrane (e.g., diffusion, active transport, endocytosis and exocytosis)
Fluid Mosaic Model: this model is used by biologist to explain how some molecules move into and out of cells while others cannot. The core of the membrane is made of compounds called phospholipids. The head of the phospholipid contains a phosphate group, the tails are fatty acids, and a variable organic group is attached to the phosphate head. The phosphate head is water-loving, but the lipid tails reject water. The fatty acid tails prevent soluble molecules from crossing the membrane. As mentioned above, water-soluble materials are able to enter the cell by way of the large, circular proteins that are set in the membrane. The large globular proteins are free to pass back and forth in the membrane and act as carrier molecules, carrying certain substances across the cell membrane. The scattered proteins form a pattern, or a mosaic.
Passive Transport: does not require the cell's chemical energy to move the molecules. Instead it depends on heat energy within the cell to increase the frequency with which molecules move.
- Diffusion: this is a process where molecules move from an area of greater concentration to an area of lesser concentration. One example is oxygen simply moving directly through a membrane in response to the high-to-low concentration gradient. The following are different types of diffusion-
- Facilitated Diffusion: useful because substances are sometimes too large to move freely through a membrane. Or they need to move against a concentration gradient. Transport proteins assists with the passage. In most cases, the transport protein creates a chemical channel for the passage of a specific substance. An example is glucose moving through with a glucose-transporter protein as it passes through the red blood cell into a body cell.
- Osmosis: this is the movement of water across a semipermeable membrane. Similar to diffusion except that it refers only to water diffusing through a permeable membrane. Water as a solvent moves from an area of high to low concentration. Or from an areas of low-solute to a high-solute concentration until the concentration is equal. The solution that has a high-solute concentration is a hypotonic solution, low-solute concentration is a hypertonic solution. Water will continue to move from low-solute to high-solute until both sides are isotonic (equal). An example is the large intestine reabsorbing water by osmosis to help maintaining water concentration to prevent the body from dehydrating. In a hypertonic solution, because there is a higher concentration of water inside the cell than outside, the water will flow from an area of high concentration to an area of low which will cause a loss of water in the cell. This causes the cell to shrivel. In animals it is called crenation and in plants it is called plasmolysis (shrinking of the protoplasm away from the cell wall of a plant).
Active Transport: this requires the use of chemical energy that is stored in ATP molecules in the cell. Types:
- Endocytosis: there are two types-
- Pinocytosis: fluid molecules are engulfed by cells through the formation of vesicles in the cell membrane.
- Phagocytosis: process of solid particles being ingested by cells
Exocytosis: this is when molecules are forced out of cells. Carried to the cell's surface by vacuoles or vesicles.
c. Explain the role of semipermeable membranes in cellular communication
A healthy membrane is selectively permeable because it allows substances needed for cell prosperity to enter and works to prohibit the penetration of unwanted and unfriendly substances. Sadly, this system is not always fool-proof and sometimes unwanted substances do pass through the membrane.
By using electron microscope images, it was observed that the embedded molecules can move sideways throughout the membrane, which is a fluid, not a solid. The membrane also has glycoproteins attached to the surface. The glycoprotein is a molecule that is used as an identification for proteins seeking a particular site for bonding. Each cell has a particular glycoprotein structure based on its need to attract or repel membrane traffic.
The proteins in the cell membrane are involved in a cellular communication. They receive chemical messages from other cells which is called signaling molecules. When these molecules bind with the proteins, they trigger a change in the protein. This causes a message to be sent into the cell and activate a specific cellular response.
The proteins embedded in the membrane serve many functions such as holding the membrane in a regular structure for easy bonding. They also function as receptor sites. In some cases the receptor protein is also a signal transducer that begins a series of enzyme-catalyzed reactions to stimulate a particular reaction within the cell. Transport proteins help substances move across the membrane. Many cell membrane proteins are multi-taskers as there are so many functions to perform. Sounds like my job as a teacher!
d. Explain the role of the endoplasmic reticulum and Golgi apparatus in the secretion of proteins
Discovered by the Italian biologist Camillio Golgi in 1898.
If a protein, or other substances, needs to be shipped outside the cell, transport vesicles travel to the Golgi apparatus. This organelle is responsible for packing up this shipment. The Golgi apparatus consists of flattened membrane-enclosed sacs. When it receives vesicles and their fluids from membranes of the endoplasmic reticulum, it will rewrap these vesicles in membranes by the Golgi body to form a shipping vesicle. It will also chemically mark them for destination points. It moves to the outer plasma membrane and fuses with it. The cellular products inside the vesicle either joins the membrane or continues to the cell's exterior. When they are shipped out of the cell, the products are referred to as secretions. Plants have several hundred Golgi bodies, animal cells usually around 10 to 20.
e. Explain the role of chloroplasts in obtaining and storing usable energy
Chloroplasts belongs to a group of structures which have the general name plastids. Plastids are membrane-bound and are found only in plants. Typically, they are free floating in the cytoplasm and hold pigment molecules or starch. Chloroplasts contain the green pigment chlorophyll. This is a special molecule that has the ability to trap light and convert it to a form of energy that plants can use to carry out the chemical steps in making food. This process is known as photosynthesis.
Chloroplasts are surrounded by a double membrane. Inside are flattened sacs called thylakoids. The thylakoids contain chlorophyll and it is here where photosynthesis takes place. Stroma is also found in the thylakoid sacs and is the dense ground substance that cushions the thylakoids.
Photosynthesis: the raw materials for photosynthesis are carbon dioxide and water. On the membrane of the thylakoids, chlorophyl and the accessory pigments are organized into functional groups called photosystems. Each of these photosystems has a reaction center or a light trap where special chlorophyl a molecule traps light energy. Two photosystems are used: Light Reaction and Dark Reaction (aka Calvin Cycle). Carbon dioxide enters and oxygen exits from the plan through adjustable openings on the underside of leaves called the stomata. Photosynthesis is an oxidation-reduction (redox) type of reaction. Reduction is the addition of an electron to an acceptor molecule. Oxidization is the removal of an electron from a molecule. Reduction stores energy in a compound and oxidation releases energy. When one substance is reduce, another is oxidized.
Photosyntheses can be described in two stages (as mentioned above), the light reaction and the dark reaction.
Light Reaction: occurs in the thylakoid's membrane. Light strikes the pigment and is captured. This light energy is absorbed by the chlorophyl molecules and transferred to make high-energy electrons. A pigment-protein complex captures the energy from the excited electrons and absorbs a water molecule. This water molecule splits apart to produce hydrogen, which is used from the energy-generating steps. Oxygen is released. The pigment, cytochrome, transfers the electrons to a second photosystem while pumping protons across the thylakoid membrane. The resulting proton gradient drives the formation of ATP. The electrons move to the dark reactions, where they are used to produce glucose.
Dark Reaction: as you may have guessed, this takes place even if no light is present. Uses energy from the light reaction to make sugar molecules. These fuel every other reaction in the cell. The cell consumes carbon dioxide and builds these to make glucose.
Animal cells do not have chloroplasts as these organisms do not make their own flood.
f. Explain the role of mitochondria in cellular respiration
As a runner, I have come to appreciate and respect the very important organelle, the mitochondrion! The mitochondrion is surrounded by a double membrane. It has a membrane of many folds fitted into its internal structure. These folds are covered with enzymes that are necessary for chemical reactions that release energy. The internal membranes is called the cristae and it forms compartments that provide additional work and storage areas for the complex task of cellular respiration. Each membrane consists of layers of protein and lipid molecules. The respiratory chain system is associated with the protein layer while the process of oxidative phophorylation involves the lipid layers.
Cellular respiration is a pathway of decomposition where it is a series of reactions that break down sugars, releasing energy along the way.
The oxygen system cannot be used directly as a source of energy but it does produce ATP in large quantities from sources in the body. Through a complex series of reactions metabolic by-products of carbohydrate, fat, or protein combine with oxygen to produce energy, carbon dioxide, and water.
Energy respiration is produced during two major phases:
anaerobic respiration: this process takes place in the cytoplasm and begins with the glucose molecule. With the assistance of enzymes, glucose is converted through a series of steps to form pyruvic acid. Throughout these steps either a hydrogen atom is given up or a water molecule is formed. When a hydrogen bond is broken, energy within that molecule becomes a bit more concentrated and is ultimately released to ADP molecules and stored between phosphate bonds. Whenever ADP accepts energy, inorganic phosphate is attached to the ADP forming ATP. There is a net gain of 2 ATPs.
aerobic respiration: this phase of cellular respiration takes place in mitochondria. The whole series of events of oxidate energy production primarily involves aerobic processing of carbohydrates and fats through the Kreb cycle and the electron transfer system. The process begins with pyruvic acid which is converted into acetyl coenzyme A. Fuel molecules are broken apart through chemical changes which releases a great deal of energy that has been stored in ATP molecules. The hydrogen atoms that were formed during glycolysis and aerobic respiration then enters the oxidate phosphorylation stage. These hydrogen atoms are passed along the electron transport chain which is found in the mitochondria's membrane. The hydrogen protons are pushed to the outside of the membrane which establishes an electrochemical gradient across the membrane. Energy resulting from the difference in potional across the membrane is used to form ATP. At the end of the electron transfer
So, the more mitochondria that an athlete possess, the better his or her endurance performance! Since running is an aerobic activity, the mitochondria is our aerobic engines that power this activity.
g. Explain the role of enzymes in chemical reactions and describe an experiment to test the catalytic role of enzymes and factors that affect enzyme activity (e.g., levels of protein organization, temperature, ionic conditions, concentration of enzyme and substrate, pH)
I love how one of my biology professors once described enzymes as a catalyst. I'm going to paraphrase her embellished story here but she said, "As a mom, I am trying to get my son out the door in the morning to catch the school bus. As I open the door, I use my foot to nudge him to hurry out the door. My foot doesn't fuse with my son or was consumed in the process. I kept my foot intact, but it did speed up the process of getting him out to the school bus." Okay, so obviously, she didn't physically use her foot to push her son out of the house so that he can catch the bus, but this little humorous imagery did help to firmly implant in my mind the role of enzymes as a catalyst.
Enzymes function as a catalyst to increase the rate of virtually all chemical reaction that take place in a living organism. Enzymes are not consumed and are constantly reused to catalyze the same specific reaction. Most enzymes are proteins and function is specific to their structure.
Enzymes depend on the correct structural alignment and orientation at the active site of the protein and the appropriate site of the reactants, called substrate, before the reaction can proceed. This geometric interaction is referred to as the lock-and-key model (first suggested by Emil Fischer in 1894). If a key and lock do not match, an action will not work- you cannot open the lock. So, the active site for the enzyme and the appropriately match site of the substrate must physically join before a reaction can occur, which is why the structure of the enzyme is important. The correct alignment and orientation must occur in order to connect the molecules.
Once the products in the reaction are formed, the enzyme is released to catalyze the same reaction for another substrate of the same type of molecule.
Denature of the enzyme may occur if it is heated which causes a change in shape, preventing it from performing its function.
h. Explain anabolic and catabolic pathways involved in the metabolism of macromolecules (e.g., polysaccharides, nucleic acids, proteins, lipids)
Metabolism involves two fundamental process:
- Anabolism: this is a building-up process, or constructive metabolism. Complex food particles are synthesized from basic nutrients. For someone who is active, this may mean an increase in their muscle mass when they work out. Or for the endurance athlete to better their oxygen usage, this may mean an increase in the amount of cellular enzymes. In order for anabolism to occur, energy must be used.
- Catabolism: this is the tearing-down process and involves the disintegration of body compounds into simpler components. For example, the breakdown of muscle glycogen to glucose and eventually carbon dioxide, water, and energy is an example of a catabolic process. The energy that is released from a catabolic process is used to support the energy needs of anabolism.
Integration and Control of Human Organ Systems
a. Relate the complementary activity of major body systems (e.g., circulatory, digestive, respiratory, excretory) to provide cells with oxygen and nutrients and remove waste products
Circulatory System: The overall functions of the circulatory system:
Respiratory System: Consists of external breathing and internal respiration. Breathing takes in air and lets out carbon dioxide and water vapor. Works close with the circulatory system.
Internal respiration (cellular respiration) takes place in cells and involves a series of biochemical events where energy is released from food molecules.
Digestive System: Begins with the mouth and ends with the anus. This system carries out five jobs that have to do with processing and distributing nutrients.
Excretory System: This system works to expel waste produced through metabolic activities. Related to the digestive system. It handles the metabolic wastes and maintains the water balance for an organism.
Lungs excrete carbon dioxide and water.
Skin excretes water and salts from the sweat glands and a small amount of oil from the sebaceous glands.
The liver contributes to the excretory system by breaking down waste and excess proteins into urea. This process is called deamination.
The urinary system is in charge of the major work of excretion.
The systems work together to ensure that the body works smoothly. Homeostasis is a term used to describe the maintenance of normal internal environment so that the body has the proper distribution and use of water, hormones, electrolytes, and other substances that are essential for life processes. This process works through a series of feedback devices. If these feedback devices are functioning properly, then the body is able to maintain normal physical and chemical composition. For example, let's say you become dehydrated. The blood will become more concentrated (hypertonic). Because maintenance of normal blood volume is very important, the blood tends to draw water from the body cells. Some cells in the hypothalamus, called osmoreceptors, are sensitive to changes in osmotic pressure. These cells then react to the more concentrated body fluids by releasing a hormone (antidiuretic hormone) from the pituitary gland. This hormone travels through the blood to the kidneys and directs them to reabsorb more water. As a result, urinary output of water is diminished.
b. Explain and analyze the role of the nervous system in mediating communication between different parts of the body and the body’s interactions with the environment
The primary function of the nervous system is to permit communication between the external and internal environments. The communication in the nervous system is made possible by signals or impulses that are carried in a one-way direction along nerve cells. The impulses are electrical or chemical.
The only things involved in a simple reflex, also known as reflex arc, are the sensory nerves, spinal cord, and motor nerves. A simple reflex allows instantaneous response without involving transmission to and from the brain. One example is pulling your hand away from a hot stove. As soon as you touch the hot stove, sensory nerves pick up the stimulus from the receptors in the skin and transmit it to the spinal cord. This signals the motor nerves to signal the muscles for you to pull your hand away. This is all done instantaneously.
Hormones works with the nervous system. For example, the digestive system. Insulin is a hormone that facilitates the uptake and the utilization of glucose by various tissues in the body- most notably, the muscles and fat tissue. As the body digests certain food, insulin is released from the pancreas. Foods with a high glycemic index may lead rapidly to high blood glucose levels which causes an enhanced secretion of insulin from the pancreas. Foods with lower glycemic index will lead to a slower insulin response and a more stable blood glucose level. Blood glucose is used particularly by the brain and other parts of the nervous system that relies on glucose for their metabolism. In fact, the brain is one of the few organs which must use considerable glucose for fuel and a lack of availability of glucose could be detrimental. Hypoglycemia (low blood glucose level) can lead to an impairment in the normal function of the brain. Hyperglycemia is high blood glucose level and can lead to damage to nerves, blood vessels, and organs. In the late 1960's, evidence began accumulating, suggesting that the nervous system can influence insulin secretion.
c. Explain the homeostatic role of the major organs (e.g., kidneys, heart, brain)
The human body has developed a number of physiological systems, called feedback systems, to regulate most body processes. For example, food intake. As the stomach expands while a person is eating a meal, nerve impulses are sent from the receptors in the stomach wall to the hypothalamus to help suppress food intake.
Kidneys: there are about a million microscopic units in the kidneys called nephron that work to actively remove waste products from the blood and return water, glucose, sodium ions and chloride ions to the blood.
Liver: breaks down waste and excess proteins to produce urea in a process called deamination. It regulates the composition of the blood as well as removes toxins from the blood.
Brain: contains neurons dedicated to monitoring and controlling specific physiological processes. There are separate groups of neurons that work to control the heart rate, temperature, and so on.
d. Explain the function of feedback loops in the nervous and endocrine systems to regulate conditions in the body and predict the effects of disturbances on these systems
To maintain an internal, stable environment (homeostasis), our body uses feedback loops to maintain a constant value, called set point. In a negative loop system, you move towards the target set point. The bigger the change, the bigger the corrective mechanism. In a positive feedback loop system you move away from that target set point.
Temperature, for example, is maintained by feedback loop. We use a negative feedback loop to maintain a constant temperature. So, if a person has a high temperature, the hypothalamus will sense the temperature change. If we get too hot, then the heat loss center of the hypothalamus is stimulated and if we are to get too cold, then the heat conservation center of the hypothalamus is stimulated. If are too hot, then our body will respond such as sweating to cool off. Our temperature may drop too far and we may become cold. We may get goosebumps, for example. Our body will then work to increase the temperature. Our body does this on a daily basis to maintain a stable body temperature. The set level is never perfectly maintained, but constantly oscillates about the set point.
A positive feedback is not maintained on a long period of time and is used when we want something to happen quickly, such as child birth. During labor, a hormone, oxytocin, is released that speeds up contractions. The increase in contractions causes more oxytocin to be released and the cycle continues until the baby is born. Another example is getting a rash from poison oak (happened to me way too many times!). You know you shouldn't scratch it, but it itches. So you scratch it. But the scratching makes it itch even more, and can even spread the rash. The more you scratch, the more it itches. Ugh. Another example of positive feedback in nature, is ice. Ice has a higher reflectivity than, say, soil. As the ice expands, more solar radiation is reflected back into space and less is absorbed by the surface. So the temperature decreases. Cooler temperature leads to more ice growth, which leads to more reflection of solar radiation back into space, and so on.
e. Explain the role of hormones (e.g., digestive, reproductive, osmoregulatory) in providing internal feedback mechanisms for homeostasis at the cellular level and in whole organisms
The endocrine is a series of ductless glands that secretes hormones. Being a ductless gland means that the endocrine system does not discharge their secretions directly into another organ, like the salivary gland delivers saliva directly in the mouth. The endocrine, instead, delivers the hormones into the blood stream. The hormones travel through the bloodstream to their target organs. Hormones regulate many important metabolic activities of cells and organs.
The endocrine system is made up of the:
pituitary gland- located in the base of the brain, exerts control over much of the functioning of the other endocrine glands. Does this through trophic hormones.
thyroid gland
parathyroid glands
adrenal gland
isles of Langerhans in the pancreas
thymus gland
pineal gland
gonads (testes in males, ovaries in females)
The main control center is the hypothalamus, which sends messages to the pituitary gland, which in turn releases hormones that regulate body functions. The endocrine system and the nervous system are closely associated and are collectively called the neuroendocrine system.
Many of the endocrine glands are linked to neural control centers by homeostatic feedback mechanisms. As discussed in the last section, the feedback system includes the positive and the negative feedback loop. Most of the endocrine glands are under the control of the negative feedback mechanisms.
An example of the homeostatic, negative feedback loop with hormones is the regulation of the blood calcium level. The parathyroid glands regulates the amount of calcium in the blood. The parathyroid gland will stimulate calcium to release from the bones and increase calcium uptake into the bloodstream from the kidneys. Now, if the blood calcium increases too much, then the parathyroid glands will reduce the parathyroid hormone production.
f. Describe the role of the musculo-skeletal system in providing structure, support, and locomotion to the human organism
The skeletal System: the primary purpose of the skeleton is to carry the weight of the body and to support and protect the internal organs. The skeleton must be strong and able to absorb reasonable amounts of shock without fracturing. The skeleton must also be flexible and light in order to permit movement. About 20% of the bone is water and 80% is mineral and protein. The bone also contains living cells and blood vessels. The production of new bone and the repair of broken bone is called osteoblasts. The break down of bone is called osteoclast. The destructive work of the osteoclast is often followed by the constructive work of the osteoblast. The skeleton bones move in response to the muscles, which work like levers allowing many different types of movement to occur such as running, jumping, bending, skipping, etc.
The Muscular System: represents 40% of the total weight of the human body. The muscle tissue is characterized by contractility and electrical excitability. Three types of muscle tissue:
Smooth: found in the walls of internal organs and do not respond to the will of the person, thus are involuntary muscles.
Striated: voluntary muscle or skeletal muscle. Located in legs, arms, back, torso. Attach to and move the skeleton.
Cardiac: only present in the heart. Contracts independently of nerve supply since reflex activity and electrical stimuli are contained within the cardiac muscle cells themselves.
Circulatory System: The overall functions of the circulatory system:
- exchange of oxygen and carbon dioxide (working with the respiratory system), oxygen being essential in cellular respiration
- distribute digested nutrients to the cells (works with the digestive system), these nutrients that are carried through the bloodstream are taken to the cells where they will undergo cellular respiration to form energy (ATP)
- distribute heat for endothermic animals
- transport hormones from their manufacturing spot to their action location
- removes waste- waste is carried by the circulatory system but is expelled by the respiratory and excretory systems
- regulates water
- fight infections
Respiratory System: Consists of external breathing and internal respiration. Breathing takes in air and lets out carbon dioxide and water vapor. Works close with the circulatory system.
Internal respiration (cellular respiration) takes place in cells and involves a series of biochemical events where energy is released from food molecules.
Digestive System: Begins with the mouth and ends with the anus. This system carries out five jobs that have to do with processing and distributing nutrients.
- takes in food- the saliva in the mouth contains an enzyme called salivary amylase (ptyalin) which begins the digestion.
- transport food to organs for temporary storage
- controls the mechanical breakdown of food and its chemical digestion
- absorption of nutrient molecules- The vast majority of nutrients are absorbed in the small intestine. Some substances are absorbed by diffusion. In facilitated diffusion, a receptor in the cell membrane is need to transport the substance from the intestine into the villi, which line the small intestine. In Active transport, energy is supplied by the villi cells in order to be absorbed. It uses enzymes made by the pancreas to digest and absorb most substances. For example, with carbohydrate, the saliva amylase initiates the digestion of the polysaccharides to disaccharide. Most of the digestion takes place in the small intestine by pancreatic amylase. These enzymes then digest the disaccharides to monosaccharides which are absorbed by the specific receptors in the villi.
- temporary storage and elimination of waste products
Excretory System: This system works to expel waste produced through metabolic activities. Related to the digestive system. It handles the metabolic wastes and maintains the water balance for an organism.
Lungs excrete carbon dioxide and water.
Skin excretes water and salts from the sweat glands and a small amount of oil from the sebaceous glands.
The liver contributes to the excretory system by breaking down waste and excess proteins into urea. This process is called deamination.
The urinary system is in charge of the major work of excretion.
The systems work together to ensure that the body works smoothly. Homeostasis is a term used to describe the maintenance of normal internal environment so that the body has the proper distribution and use of water, hormones, electrolytes, and other substances that are essential for life processes. This process works through a series of feedback devices. If these feedback devices are functioning properly, then the body is able to maintain normal physical and chemical composition. For example, let's say you become dehydrated. The blood will become more concentrated (hypertonic). Because maintenance of normal blood volume is very important, the blood tends to draw water from the body cells. Some cells in the hypothalamus, called osmoreceptors, are sensitive to changes in osmotic pressure. These cells then react to the more concentrated body fluids by releasing a hormone (antidiuretic hormone) from the pituitary gland. This hormone travels through the blood to the kidneys and directs them to reabsorb more water. As a result, urinary output of water is diminished.
b. Explain and analyze the role of the nervous system in mediating communication between different parts of the body and the body’s interactions with the environment
The primary function of the nervous system is to permit communication between the external and internal environments. The communication in the nervous system is made possible by signals or impulses that are carried in a one-way direction along nerve cells. The impulses are electrical or chemical.
The only things involved in a simple reflex, also known as reflex arc, are the sensory nerves, spinal cord, and motor nerves. A simple reflex allows instantaneous response without involving transmission to and from the brain. One example is pulling your hand away from a hot stove. As soon as you touch the hot stove, sensory nerves pick up the stimulus from the receptors in the skin and transmit it to the spinal cord. This signals the motor nerves to signal the muscles for you to pull your hand away. This is all done instantaneously.
Hormones works with the nervous system. For example, the digestive system. Insulin is a hormone that facilitates the uptake and the utilization of glucose by various tissues in the body- most notably, the muscles and fat tissue. As the body digests certain food, insulin is released from the pancreas. Foods with a high glycemic index may lead rapidly to high blood glucose levels which causes an enhanced secretion of insulin from the pancreas. Foods with lower glycemic index will lead to a slower insulin response and a more stable blood glucose level. Blood glucose is used particularly by the brain and other parts of the nervous system that relies on glucose for their metabolism. In fact, the brain is one of the few organs which must use considerable glucose for fuel and a lack of availability of glucose could be detrimental. Hypoglycemia (low blood glucose level) can lead to an impairment in the normal function of the brain. Hyperglycemia is high blood glucose level and can lead to damage to nerves, blood vessels, and organs. In the late 1960's, evidence began accumulating, suggesting that the nervous system can influence insulin secretion.
c. Explain the homeostatic role of the major organs (e.g., kidneys, heart, brain)
The human body has developed a number of physiological systems, called feedback systems, to regulate most body processes. For example, food intake. As the stomach expands while a person is eating a meal, nerve impulses are sent from the receptors in the stomach wall to the hypothalamus to help suppress food intake.
Kidneys: there are about a million microscopic units in the kidneys called nephron that work to actively remove waste products from the blood and return water, glucose, sodium ions and chloride ions to the blood.
Liver: breaks down waste and excess proteins to produce urea in a process called deamination. It regulates the composition of the blood as well as removes toxins from the blood.
Brain: contains neurons dedicated to monitoring and controlling specific physiological processes. There are separate groups of neurons that work to control the heart rate, temperature, and so on.
d. Explain the function of feedback loops in the nervous and endocrine systems to regulate conditions in the body and predict the effects of disturbances on these systems
To maintain an internal, stable environment (homeostasis), our body uses feedback loops to maintain a constant value, called set point. In a negative loop system, you move towards the target set point. The bigger the change, the bigger the corrective mechanism. In a positive feedback loop system you move away from that target set point.
Temperature, for example, is maintained by feedback loop. We use a negative feedback loop to maintain a constant temperature. So, if a person has a high temperature, the hypothalamus will sense the temperature change. If we get too hot, then the heat loss center of the hypothalamus is stimulated and if we are to get too cold, then the heat conservation center of the hypothalamus is stimulated. If are too hot, then our body will respond such as sweating to cool off. Our temperature may drop too far and we may become cold. We may get goosebumps, for example. Our body will then work to increase the temperature. Our body does this on a daily basis to maintain a stable body temperature. The set level is never perfectly maintained, but constantly oscillates about the set point.
A positive feedback is not maintained on a long period of time and is used when we want something to happen quickly, such as child birth. During labor, a hormone, oxytocin, is released that speeds up contractions. The increase in contractions causes more oxytocin to be released and the cycle continues until the baby is born. Another example is getting a rash from poison oak (happened to me way too many times!). You know you shouldn't scratch it, but it itches. So you scratch it. But the scratching makes it itch even more, and can even spread the rash. The more you scratch, the more it itches. Ugh. Another example of positive feedback in nature, is ice. Ice has a higher reflectivity than, say, soil. As the ice expands, more solar radiation is reflected back into space and less is absorbed by the surface. So the temperature decreases. Cooler temperature leads to more ice growth, which leads to more reflection of solar radiation back into space, and so on.
e. Explain the role of hormones (e.g., digestive, reproductive, osmoregulatory) in providing internal feedback mechanisms for homeostasis at the cellular level and in whole organisms
The endocrine is a series of ductless glands that secretes hormones. Being a ductless gland means that the endocrine system does not discharge their secretions directly into another organ, like the salivary gland delivers saliva directly in the mouth. The endocrine, instead, delivers the hormones into the blood stream. The hormones travel through the bloodstream to their target organs. Hormones regulate many important metabolic activities of cells and organs.
The endocrine system is made up of the:
pituitary gland- located in the base of the brain, exerts control over much of the functioning of the other endocrine glands. Does this through trophic hormones.
thyroid gland
parathyroid glands
adrenal gland
isles of Langerhans in the pancreas
thymus gland
pineal gland
gonads (testes in males, ovaries in females)
The main control center is the hypothalamus, which sends messages to the pituitary gland, which in turn releases hormones that regulate body functions. The endocrine system and the nervous system are closely associated and are collectively called the neuroendocrine system.
Many of the endocrine glands are linked to neural control centers by homeostatic feedback mechanisms. As discussed in the last section, the feedback system includes the positive and the negative feedback loop. Most of the endocrine glands are under the control of the negative feedback mechanisms.
An example of the homeostatic, negative feedback loop with hormones is the regulation of the blood calcium level. The parathyroid glands regulates the amount of calcium in the blood. The parathyroid gland will stimulate calcium to release from the bones and increase calcium uptake into the bloodstream from the kidneys. Now, if the blood calcium increases too much, then the parathyroid glands will reduce the parathyroid hormone production.
f. Describe the role of the musculo-skeletal system in providing structure, support, and locomotion to the human organism
The skeletal System: the primary purpose of the skeleton is to carry the weight of the body and to support and protect the internal organs. The skeleton must be strong and able to absorb reasonable amounts of shock without fracturing. The skeleton must also be flexible and light in order to permit movement. About 20% of the bone is water and 80% is mineral and protein. The bone also contains living cells and blood vessels. The production of new bone and the repair of broken bone is called osteoblasts. The break down of bone is called osteoclast. The destructive work of the osteoclast is often followed by the constructive work of the osteoblast. The skeleton bones move in response to the muscles, which work like levers allowing many different types of movement to occur such as running, jumping, bending, skipping, etc.
The Muscular System: represents 40% of the total weight of the human body. The muscle tissue is characterized by contractility and electrical excitability. Three types of muscle tissue:
Smooth: found in the walls of internal organs and do not respond to the will of the person, thus are involuntary muscles.
Striated: voluntary muscle or skeletal muscle. Located in legs, arms, back, torso. Attach to and move the skeleton.
Cardiac: only present in the heart. Contracts independently of nerve supply since reflex activity and electrical stimuli are contained within the cardiac muscle cells themselves.
Physiology of the Immune System
a. Explain the humoral response to infection
The human immune response system embraces two major biochemical events:
The humoral immune response
The cell-mediated response
The second line of defense (first line is the skin) is made possible by a type of white blood cell known as a lymphocyte. The two kinds:
B-cell lymphocyte- participates in the humoral immune response, matures in the bone marrow (thus the name B-cell), rough ER due to large number of ribosomes attached to the membranes, each B-cell has its own membrane bound antibody and carry out specific antigen-recognition proteins
T-cell lymphocyte- participates in the cell mediated response, matures in the thymus gland (hence the name T-cell), large concentration of free ribosomes in the cytoplasm
These two types of cells work together to carry out a complex series of events known as the immune system. Look alike in the inactive state, but differ significantly when activated.
The humoral immune response works to deal with invading microbes and involves the production of protein molecules called antibodies. The cell-mediated response demands direct cellular action. The cells of the immune system are able to recognize and take action upon microorganisms and foreign substances that enter the body. Each of these responses is driven by a specific type of lymphocyte cell (produced by stem cells), either the B-cell or the T-cell.
The humoral immune response is an antibody-mediated response involves macrophages that recognizes a specific antigen or pathogen traveling in the lymph or bloodstream. The antigen gets engulfed by a macrophage. How do these cells know what invader to engulf? Think of all cells and microbes wearing a uniform, these molecules that cover their surface. These molecules are unique. So, say an invading army of yellow fever viruses get into a person's body, they are going to display a different marker molecules that is unique to them. The macrophages and other cells in your body uses these markers to identify the cells that belongs to your body and those that are harmless bacteria, against those that are harmful and need to be destroyed. Those molecules on the invading microbe that stimulates the immune system are called antigens.
Helper T-cells will send out an SOS to other cells of the immune system. The T-cell receptor will bond to the microbes antigen, activating it. It will either become effector T-cells or memory T-cells. It is the effector T-cells that sends out the SOS by releasing cytokines.
The other type of T-cells are Cytotoxic T-cells- MHC I attracts cytotoxic T-cells. Once a cytotoxic T-cell finds a problem cell, whether it was infiltrated by a pathogen or is cancerous, it gets activated, divides, and differentiates into either memory or effector T-cells (does the killing of the problem cell.) May release enzymes that causes the cell to kill itself.
You can think of B-cells as weapon factories- with the help of T-cells, they are able to produce antibodies ("Y" shape) that binds to the antigens on the surface of microbes. These specialized defender cells B-cells will create antibodies, which are proteins. The B-cell will become activated. Now activated, it will begin to proliferate and take on either one of the two roles: B-cells can either become memory cells or plasma cells (also called effector cells). Plasma cells work to produce tons of antibodies that will uniquely be able to bind with the pathogen. The antibodies are released and circulate through the body, bonding to antigens. Or, they will become memory cells that provide future immunity.
Info about MHC: MHC (major histocompatibility complex) are found on the surface of cells that help by binding peptide fragments derived from pathogens and display them to help immune system recognize the foreign substances. There are two major classes of MHC molecules:
MHC class I- these are found in almost every cell (very nucleic cell) of an organism. Function is to bind endogenous antigens synthesized in the cell. MCH class I presents antigen to cytoxic T-cell lymphocytes. Binds CD8 adhesion molecules on cytoxic T-cells.
MCH class II- these are restricted to the cells of the immune system called macrophages and lymphocytes. Antigen presenting cells ingest foreign antigens either through phagocytosis or endocytosis and break it down into peptide fragments that bind to MHC class II molecules to be then recognized by the Helper T-cells. The T-cells bind to the MHC II with the help of CD4 (protein receptor found on the surface of the T cells). Once bound, the T-cell becomes active, begins to proliferate, and secrete cytokines.
b. Compare cell mediated and humoral responses to infection
Humoral response involves the use of antibodies that were produced by B-cells and Helper T-cells in order to attack invading foreign substances. Production of memory cells also occurs in order to help with a faster response in case of another infection.
Cell-mediated response involves Cytotoxic T-cells that kills cells that are no longer working properly.
c. Explain how vaccination works and distinguish among variables affecting success rate
Vaccines take advantage of the body's ability to learn how to eliminate almost any disease-causing germ. As described in section a, your body will remember how to protect itself from a particular microbe (such as the production of memory cells). Vaccines are also very important in the case of powerful, invading microbes that can overwhelm the body's natural defense system.
Vaccines are made by using microbes that have been killed or weakened and injecting it into humans. This injected substance activates the body's immune system to defend against these antigens.The body is prepared to fight the actual pathogen in a future if an actual intrusion of this microbe were to occur.
If a large number of people within a community are vaccinated against a particular disease, then the likelihood of getting that particular disease becomes less and less. However, if too many people are not vaccinated, then the disease can reappear. The measles outbreak in the 1980's is one example of an outbreak that resulted in thousands of cases and a little over 100 measles related deaths.
No vaccine is perfectly safe. For example, there is a chance that the person will end up with the disease once getting the vaccine. Or they may have a reaction to the vaccine.
d. Predict the consequences of a compromised immune system [e.g., AIDS (Acquired Immune Deficiency Syndrome)]
The HIV attacks the CD4 lymphocytes, which function as the helper cells. When they are made inactive, then the T-helper cells are unable to stimulate the reproduction of the B-cell lymphocytes. The B-cells produce antibody-producing plasma and memory cells. The result is that being infected with HIV causes the immune system to collapse, leaving the person open to devastating infections.
AIDS shuts down the entire immune system. The person is left host to a number of infectious organisms that causes diseases.
The human immune response system embraces two major biochemical events:
The humoral immune response
The cell-mediated response
The second line of defense (first line is the skin) is made possible by a type of white blood cell known as a lymphocyte. The two kinds:
B-cell lymphocyte- participates in the humoral immune response, matures in the bone marrow (thus the name B-cell), rough ER due to large number of ribosomes attached to the membranes, each B-cell has its own membrane bound antibody and carry out specific antigen-recognition proteins
T-cell lymphocyte- participates in the cell mediated response, matures in the thymus gland (hence the name T-cell), large concentration of free ribosomes in the cytoplasm
These two types of cells work together to carry out a complex series of events known as the immune system. Look alike in the inactive state, but differ significantly when activated.
The humoral immune response works to deal with invading microbes and involves the production of protein molecules called antibodies. The cell-mediated response demands direct cellular action. The cells of the immune system are able to recognize and take action upon microorganisms and foreign substances that enter the body. Each of these responses is driven by a specific type of lymphocyte cell (produced by stem cells), either the B-cell or the T-cell.
The humoral immune response is an antibody-mediated response involves macrophages that recognizes a specific antigen or pathogen traveling in the lymph or bloodstream. The antigen gets engulfed by a macrophage. How do these cells know what invader to engulf? Think of all cells and microbes wearing a uniform, these molecules that cover their surface. These molecules are unique. So, say an invading army of yellow fever viruses get into a person's body, they are going to display a different marker molecules that is unique to them. The macrophages and other cells in your body uses these markers to identify the cells that belongs to your body and those that are harmless bacteria, against those that are harmful and need to be destroyed. Those molecules on the invading microbe that stimulates the immune system are called antigens.
Helper T-cells will send out an SOS to other cells of the immune system. The T-cell receptor will bond to the microbes antigen, activating it. It will either become effector T-cells or memory T-cells. It is the effector T-cells that sends out the SOS by releasing cytokines.
The other type of T-cells are Cytotoxic T-cells- MHC I attracts cytotoxic T-cells. Once a cytotoxic T-cell finds a problem cell, whether it was infiltrated by a pathogen or is cancerous, it gets activated, divides, and differentiates into either memory or effector T-cells (does the killing of the problem cell.) May release enzymes that causes the cell to kill itself.
You can think of B-cells as weapon factories- with the help of T-cells, they are able to produce antibodies ("Y" shape) that binds to the antigens on the surface of microbes. These specialized defender cells B-cells will create antibodies, which are proteins. The B-cell will become activated. Now activated, it will begin to proliferate and take on either one of the two roles: B-cells can either become memory cells or plasma cells (also called effector cells). Plasma cells work to produce tons of antibodies that will uniquely be able to bind with the pathogen. The antibodies are released and circulate through the body, bonding to antigens. Or, they will become memory cells that provide future immunity.
Info about MHC: MHC (major histocompatibility complex) are found on the surface of cells that help by binding peptide fragments derived from pathogens and display them to help immune system recognize the foreign substances. There are two major classes of MHC molecules:
MHC class I- these are found in almost every cell (very nucleic cell) of an organism. Function is to bind endogenous antigens synthesized in the cell. MCH class I presents antigen to cytoxic T-cell lymphocytes. Binds CD8 adhesion molecules on cytoxic T-cells.
MCH class II- these are restricted to the cells of the immune system called macrophages and lymphocytes. Antigen presenting cells ingest foreign antigens either through phagocytosis or endocytosis and break it down into peptide fragments that bind to MHC class II molecules to be then recognized by the Helper T-cells. The T-cells bind to the MHC II with the help of CD4 (protein receptor found on the surface of the T cells). Once bound, the T-cell becomes active, begins to proliferate, and secrete cytokines.
b. Compare cell mediated and humoral responses to infection
Humoral response involves the use of antibodies that were produced by B-cells and Helper T-cells in order to attack invading foreign substances. Production of memory cells also occurs in order to help with a faster response in case of another infection.
Cell-mediated response involves Cytotoxic T-cells that kills cells that are no longer working properly.
c. Explain how vaccination works and distinguish among variables affecting success rate
Vaccines take advantage of the body's ability to learn how to eliminate almost any disease-causing germ. As described in section a, your body will remember how to protect itself from a particular microbe (such as the production of memory cells). Vaccines are also very important in the case of powerful, invading microbes that can overwhelm the body's natural defense system.
Vaccines are made by using microbes that have been killed or weakened and injecting it into humans. This injected substance activates the body's immune system to defend against these antigens.The body is prepared to fight the actual pathogen in a future if an actual intrusion of this microbe were to occur.
If a large number of people within a community are vaccinated against a particular disease, then the likelihood of getting that particular disease becomes less and less. However, if too many people are not vaccinated, then the disease can reappear. The measles outbreak in the 1980's is one example of an outbreak that resulted in thousands of cases and a little over 100 measles related deaths.
No vaccine is perfectly safe. For example, there is a chance that the person will end up with the disease once getting the vaccine. Or they may have a reaction to the vaccine.
d. Predict the consequences of a compromised immune system [e.g., AIDS (Acquired Immune Deficiency Syndrome)]
The HIV attacks the CD4 lymphocytes, which function as the helper cells. When they are made inactive, then the T-helper cells are unable to stimulate the reproduction of the B-cell lymphocytes. The B-cells produce antibody-producing plasma and memory cells. The result is that being infected with HIV causes the immune system to collapse, leaving the person open to devastating infections.
AIDS shuts down the entire immune system. The person is left host to a number of infectious organisms that causes diseases.
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