AP BIO Unit 4

What occurs with an ion channel receptor after binding to a ligand?

It will either open or close to let ions in or out.

Identify a message communicated by direct cell-to-cell contact. What occurs during this process?

A message that is communicated by cell-to-cell contact is a paracrine message or the use of neurotransmitters. During this process a transmembrane protein is used or pathways, in animal cells called gap junctions, and in plant cells called plasmodesmata.

What is a second messenger? Identify two examples. What is the function of a second messenger?

A secondary messenger is an intermediate signaling molecule that will amplify a response. Two examples are cAMP (cyclic adenosine monophosphate) or protein kinases. a. The function of a second messenger is to relay a message that will produce an amplified cellular response.

What occurs during reception?

A signal molecule binds to a receptor on a target cell.

2. The diagram below shows a developing worm embryo at the four-cell stage. Experiments have shown that when cell 3 divides, the anterior daughter cell gives rise to muscle and gonads and the posterior daughter cell gives rise to the intestine. However, if the cells of the embryo are separated from one another early during the four-cell stage, no intestine will form. Other experiments have shown that if cell 3 and cell 4 are recombined after the initial separation, the posterior daughter cell of cell 3 will once again give rise to normal intestine. Which of the following is the most plausible explanation for these findings? a. A cell surface protein on cell 4 signals cell 3 to induce formation of the worm's intestine. b. The plasma membrane of cell 4 interacts with the plasma membrane of the posterior portion of cell 3, causing invaginations that become microvilli.

A. A cell surface protein on cell 4 signals cell 3 to induce formation of the worm's intestine.

8. ADH is important in maintaining homeostasis in mammals. ADH is released from the hypothalamus in response to high tissue osmolarity. In response to ADH, the collecting duct and distal tubule in the kidney become more permeable to water, which increases water reabsorption into the capillaries. The amount of hormone released is controlled by a negative feedback loop. Based on the model presented, which of the following statements expresses the proper relationship between osmolarity, ADH release, and urine production? a. As tissue osmolarity rises, more ADH is released, causing less water to be excreted as urine. b. As tissue osmolarity rises, less ADH is released, causing less water to be excreted as urine. c. As tissue osmolarity rises, more ADH is released, causing more water to be excreted as urine. d. As tissue osmolarity rises, less ADH is released, causing more water to be excreted as urine.

A. As tissue osmolarity rises, more ADH is released, causing less water to be excreted as urine.

1. Based on your understanding of the ways in which signal transmission mediates cell function, which of the following predictions is most consistent with the information given above? a. In an environment with low fixed nitrogen, treating the Anabaena cells with a calcium-binding compound should prevent heterocyst differentiation. b. A strain that overexpresses the patS gene should develop many more heterocysts in a low fixed nitrogen environment. c. In an environment with abundant fixed nitrogen, free calcium levels should be high in all cells so that no heterocysts develop. d. In environments with abundant fixed nitrogen, loss of the hetR gene should induce heterocyst development.

A. In an environment with low fixed nitrogen, treating the Anabaena cells with a calcium-binding compound should prevent heterocyst differentiation.

5. Insulin is a protein hormone that is secreted in response to elevated blood glucose levels. When insulin binds to its receptors on liver cells, the activated receptors stimulate phosphorylation cascades that cause the translocation of glucose transporters to the plasma membrane. Based on the information provided, which of the following best describes the role of insulin in this liver cell signal transduction pathway? a. It acts as a ligand. b. It acts as a receptor. c. It acts as a secondary messenger. d. It acts as a protein kinase.

A. It acts as a ligand.

What is the process that results in the release of a chemical signal from a cell? Where are the chemical signals synthesized? Where are the chemical signals processed?

Cell signaling or exocytosis. Synthesized in the nucleus of the cell. Processed in the target cell.

How can a chemical interfere with the signaling pathway?

It may amplify a response or prevent the pathway from moving any further and cause a response to be inhibited.

What occurs with a G-protein coupled receptor after binding to a ligand

It turns GDP into GTP.

How does a cell use negative feedback to return to a target set point after a disturbance?

It uses it to know where it is supposed to stop for the ideal response. So the set point tells the pathway when and where to stop.

What causes apoptosis?

P53 proteins block mitosis if there is DNA damage, it initiates DNA to repair or signals it to perform apoptosis.

What is positive feedback? Identify two examples of positive feedback loops.

Positive feedback leads to stronger and stronger responses until the end goal is achieved. Two examples are childbirth and blood clotting.

What are the components of a signal transduction pathway?

Reception, transduction, response

20. Which of the following is the stage where the cell no longer divides? a. G0 b. G1 c. G2 d. S

A. G0

18. Which feedback mechanism involves amplifying responses and processes in biological organisms? a. Positive Feedback b. Negative Feedback

A. Positive Feedback

What is apoptosis?

Apoptosis is programmed cell death that a cell will undergo.

What occurs at the G2 checkpoint?

At the end of G2 before entering mitosis, the cell ensures that its DNA has been completely copied in preparation for nuclear division., it is the DNA replication checkpoint.

17. Which feedback mechanism involves homeostasis of a particular condition by regulating physiological processes? a. Positive Feedback b. Negative Feedback

B. Negative Feedback

21. Which of the following describes the order of the steps in mitosis? a. metaphase, telophase, anaphase, prophase b. prophase, metaphase, anaphase, telophase c. telophase, anaphase, metaphase, prophase d. prophase, anaphase, metaphase, telophase

B. prophase, metaphase, anaphase, telophase

23. Which checkpoint is responsible for ensuring nondisjunction does not take place? a. G1 checkpoint b. S checkpoint c. G2 checkpoint d. M checkpoint

D. M checkpoint

19. Which of the following is NOT a stage of the cell cycle? a. interphase b. cytokinesis c. mitosis d. apoptosis

D. apoptosis

How is cytokinesis different in a plant versus an animal?

In an animal cell's cytokinesis, the membranes pinch off in the middle to separate the daughter cells. In a plant cell's cytokinesis, they form a membrane between the dividing cells and make a new length of cell wall.

Using an example, explain how positive feedback can be used to maintain homeostasis?

In childbirth, positive feedback is used to maintain homeostasis because as the baby pushes it causes more contractions. These contractions continue as the baby pushes on the birth canal, the contractions push the baby out until nothing is pressing on the birth canal so when the stimulus is gone, it returns to homeostasis. It removes a stimulus to return to homeostasis.

Using an example, explain how negative feedback can be used to maintain homeostasis?

In the example of blood sugar regulation, if the glucose in the blood is too low the pancreas will release glucagon. It then breaks down glycogen into glucose. It maintains homeostasis because it brings a low level back to a normal level.

How does a ligand binding to a channel cause a cellular response?

It allows the channel to open or close which lets in other ions.

How does positive feedback amplify the response? Identify one example.

It amplifies the response because as the response is produced from a stimulus, the pathway loops to create more and more of a response until the stimulus is removed. One example is breastfeeding.

Where does the ligand bind on the receptor?

It binds on a specific opening or space that the shapes match.

What would happen if there was a mutation in a transduction protein? How would this affect the response of the cell?

It can cause a mis-folding of the transduction protein. It may mean that the ligand can bind but it won't be transformed into a signal, or the signal will be amplified.

What is the function of a kinase?

It catalyzes the transfer of phosphate from ATP to proteins.

What is negative feedback? Identify two examples of negative feedback loops.

Negative feedback maintains a set point by reducing the change or response. Two examples are body temperature and blood sugar.

Identify a message communicated by chemical signaling. What occurs during this process?

Neurotransmitters communicate the message. Chemicals bind to receptors on another cell.

What is a phosphorylation cascade?

One enzyme is phosphorylated, and it leads to a pathway of multiple proteins be phosphorylated.

What occurs at the M checkpoint? What happens if the cell prematurely bypasses this checkpoint?

The cell checks to make sure each pair of sister chromatids is connected to spindle fibers so that the sister chromatids can be separated from one another in anaphase. Chromosomes won't be attached and may divide with uneven chromosome numbers in the cells.

What occurs at the G1 checkpoint?

The checkpoint late in G1 delays progression through the cell cycle by interfering with the formation of a cyclin-CDK complex until DNA damage is repaired, it checks for DNA damage.

How does the cell undergo cytokinesis?

The cytoplasm is divided and the membrane contracts and cleaves into two.

Identify the phase of mitosis that ensures identical genetic information is transferred. How does this process ensure that identical genetic information is transferred?

The phase of mitosis where genetic information is transferred is prophase. Prophase pairs identical chromatin into matching chromosomes or sister chromatids.

What are the phases of interphase? What occurs in each of these phases?

The phases of interphase are the G1 phase, the S phase, and the G2 phase. In the G1 phase, the cell starts to prepare for DNA replication, in the S phase the DNA synthesis happens which duplicates the chromosomes, and in the G2 phase, the cell prepares for the M phase.

What occurs when the ligand binds to the receptor that initiated transduction?

The receptor slightly changes shape to fit the ligand.

What is the role of the ligand in the signal transduction pathway?

The role of the ligand is to act as a signaling molecule or a signal to the target cell.

What occurs during the process of transduction?

The signaling molecule's signal is converted so it can elicit a cellular response.

What process allows for the passage of the M checkpoint?

The spindles are attached to the kinetochores properly.

What are the three phases of the cell cycle? What occurs in each of these three phases?

The three phases of the cell cycle are the M phase (mitosis), interphase, and cytokinesis. In mitosis the cell prepares to divide and divides the nucleus, in cytokinesis the cell divides into two daughter cells, in interphase it prepares for DNA replication and then duplicates and prepares for the M phase.

Identify three roles of mitosis.

The three roles of mitosis are asexual reproduction, growth of multicellular organisms, and repair of damaged cells.

What occurs with a tyrosine kinase receptor after binding to a ligand?

They phosphorylate other parts of the pathway.

How do chromosomes move through the process of mitosis?

They start as chromatin and then during the first stage of mitosis, they condense to form chromosomes. In anaphase, they are pulled apart into sister chromatids, and then in telophase uncondense back into chromatin.

How do cells communication over a long distance? Identify one example

They use hormones. a. One example of this is the use of the endocrine system.

How do cells communicate over a short distance? Identify Two examples.

They use paracrine signaling. Two examples are neurotransmitters and quorum sensing.

Why would the receptor be in different locations?

They would be in different locations because they have different polarities.

Why would a cell undergo apoptosis?

They would undergo apoptosis because they are damaged, unhealthy, or have met their lifespan.

True or False: Only specific cells will respond to specific chemical signals because they have a receptor for the chemical signal.

True

What occurs during the process of reception?

he target cell receives the signaling molecule.

Identify three possible cellular responses.

Three possible cellular responses are the opening of gated-ion channels, cell movement, synthesis of a new protein.

What is the role of the receptor in the signal transduction pathway?

1 The role of the receptor is to act as a site for a ligand to bind to.

Identify one example of a chemical that activates a signaling pathway

A chemical that activates a signaling pathway can be albuterol.

Identify one example of a chemical that inhibits a signaling pathway

A chemical that inhibits a signaling pathway can be caffeine.

9. When the wall of a blood vessel is damaged, collagen fibers in the wall are exposed to the interior of the blood vessel. The exposed fibers and chemicals released from the endothelial cells that line the blood vessel attract platelets, which start to form a plug and release other chemicals Which of the following best explains the feedback mechanism illustrated? a. This is an example of positive feedback, because the few platelets that initially bind attract more platelets to the damaged area. b. This is an example of positive feedback, because it results from the interactions among collagen, endothelial cells, and platelets. c. This is an example of negative feedback, because a large clump of platelets can block the blood vessel and prevent blood flow through it. d. This is an example of negative feedback, because the accumulation of platelets returns the open blood vessel wall to a closed state

A. This is an example of positive feedback, because the few platelets that initially bind attract more platelets to the damaged area.

15. Describe what occurs when the ligand binds to the receptor. a. confirmational change in shape of receptor b. phosphorylation of ligand c. ligand passes through the membrane d. receptor binds additional ligands

A. confirmational change in shape of receptor

24. Describe the interaction between cyclin and CdK. a. cyclin interacts with CdK to initiate the mitotic phase b. cyclin is the precursor to CdK, when synthesized allow for mitosis proceed c. cyclin acts as an inhibitor to CdK to wait for all DNA to be synthesized d. cyclin binds to CdK to initiate DNA replication

A. cyclin interacts with CdK to initiate the mitotic phase

22. Which of the following is NOT a role of mitosis? a. gametes b. tissue repair c. growth d. asexual reproduction

A. gametes

12. What are the three parts of signal transduction pathway? a. reception, transduction, response b. confirmation, transduction, transcription c. reception, amplification, transcription d. confirmation, amplification, response

A. reception, transduction, response

Identify the phase of mitosis that ensures equal transfer of chromosomes. How does this process ensure there is an equal transfer of chromosomes?

Anaphase ensures there is an equal transfer of chromosomes. It ensures it because the chromosomes are broken into their halves and move to opposite sides. So, the two ends of the cell have an equal amount.

6. The endocrine system incorporates feedback mechanisms that maintain homeostasis. Which of the following demonstrates negative feedback by the endocrine system? a. During labor, the fetus exerts pressure on the uterine wall, inducing the production of oxytocin, which stimulates uterine wall contraction. The contractions cause the fetus to further push on the wall, increasing the production of oxytocin. b. After a meal, blood glucose levels become elevated, stimulating beta cells of the pancreas to release insulin into the blood. Excess glucose is then converted to glycogen in the liver, reducing blood glucose levels. c. At high elevation, atmospheric oxygen is more scarce. In response to signals that oxygen is low, the brain decreases an individual's rate of respiration to compensate for the difference. d. A transcription factor binds to the regulatory region of a gene, blocking the binding of another transcripti

B. After a meal, blood glucose levels become elevated, stimulating beta cells of the pancreas to release insulin into the blood. Excess glucose is then converted to glycogen in the liver, reducing blood glucose levels.

3. The vertebrate forelimb initially develops in the embryo as a solid mass of tissue. As development progresses, the solid mass near the end of the forelimb is remodeled into individual digits. Which of the following best explains the role of apoptosis in remodeling of the forelimb? a. Apoptosis replaces old cells with new ones that are less likely to contain mutations. b. Apoptosis involves the regulated activation of proteins in specific cells of the developing forelimb that leads to the death of those cells. c. Apoptosis involves the destruction of extra cells in the developing forelimb, which provides nutrients for phagocytic cells. d. Apoptosis in the developing forelimb triggers the differentiation of cells whose fate was not already determined.

B. Apoptosis involves the regulated activation of proteins in specific cells of the developing forelimb that leads to the death of those cells.

How are signals amplified after reception?

By the phosphorylation cascade or signaling cascade.

16. Describe the impact of a mutation in any domain of the protein components of the transduction signaling pathway. a. receptor unable to bind to ligand b. no changes in transduction due to initial signal transduction from ligand c. alters response of the cell d. amplification of signaling pathway to bind more ligands

C. alters response of the cell

11. If chemical signals in the cytoplasm control the progression of a cell to the M phase of the cell cycle, then fusion of a cell in G1 with a cell in early M phase would most likely result in the a. replication of chromosomes only in the G1 cell b. exiting of both cells from the cell cycle and into the G0 phase c. condensation of chromatin in preparation of nuclear division in both cells d. transfer of organelles from the G1 cell to the cell in the M phase

C. condensation of chromatin in preparation of nuclear division in both cells

Identify two examples of a cell responding to its environment. What occurs in each of these examples?

Cell division and a metabolic response. In cell division they respond to signals telling them to go through their life cycle and in their metabolic responses. Metabolism is a catabolic and anabolic process which is a pathway to gain energy.

What are cyclins? What are CDKs? How do these two interact to allow passage of the G2 checkpoint?

Cyclins are groups of proteins that appear in large quantities during the cell cycle. CDKs are enzymes that bind to cyclin partners which gain the ability to transfer a phosphate group to a target protein, "cyclin-dependent kinase". Cyclins increase and bind to the CDKs which allows the cell to proceed from G2 into mitosis.

7. The diagram below illustrates feedback control as exerted by the hormone thyroxine. Following surgical removal of the thyroid gland, the level of TSH in the blood will increase. Which of the following best explains this increase? a. Residual blood thyroxine, from prior to thyroid gland removal, will bind to cells in the anterior pituitary, signaling more TSH secretion. b. Thyroxine will remain bound to thyroxine receptors on various body cells, and these body cells will secrete additional hormones that stimulate the anterior pituitary to secrete TSH. c. Thyroxine that was stored in the anterior pituitary prior to thyroid gland removal will signal more TSH secretion. d. A decrease in thyroxine levels means a loss of inhibition to the hypothalamus and anterior pituitary, leading to increased TSH secretion

D. A decrease in thyroxine levels means a loss of inhibition to the hypothalamus and anterior pituitary, leading to increased TSH secretion.

4. The figure below shows a model of a ligand precursor being cleaved to produce an active ligand that binds to a specific receptor. Which of the following is most likely to reduce the binding of the active ligand to its receptor? a. A change in the cytoskeletal attachment of transmembrane proteins b. The presence of a large amount of the precursor form of the ligand c. An increase in the ratio of the number of unsaturated to the number of saturated fatty acid tails of the membrane lipids d. A mutation in the receptor gene that causes a substitution of a charged amino acid for a nonpolar amino acid in the ligand binding site of the receptor

D. A mutation in the receptor gene that causes a substitution of a charged amino acid for a nonpolar amino acid in the ligand binding site of the receptor

10. Equal amounts of total protein were analyzed after separation by electrophoresis to identify the relative amounts of the different proteins present in each sample. The thickness of the bands indicates the relative amounts of rabbit a-hemoglobin, rabbit b-hemoglobin, and frog tubulin (a cytoskeletal protein that is expressed at relatively constant levels in all tissues) present in each tadpole sample. The experimental protocol and results are summarized in the figure below. a. Rabbit mRNA is composed of nucleotides that are more stable than those in frog mRNA. b. Rabbit hemoglobin is synthesized more efficiently than frog hemoglobin in frog cells. c. After differentiation, the rabbit hemoglobin proteins move through the circulatory system of the tadpole to every cell. d. The mRNA injected into the newly fertilized frog eggs is distributed in the cytoplasm of every daughter cell during cell division.

D. The mRNA injected into the newly fertilized frog eggs is distributed in the cytoplasm of every daughter cell during cell division.

14. Which of the following is NOT a response by the cell from a signal transduction pathway? a. cell growth b. gene expression c. secretion of molecules d. all of the above are responses

D. all of the above are responses

13. Transduction step traditionally amplifies the signal, which of the following are NOT involved with transduction? a. secondary messengers b. protein modification c. phosphorylation cascade d. ligands

D. ligands

What occurs during cytokinesis?

During cytokinesis, the cell splits into two daughter cells.

Identify three causes of cancer. How does each affect the cell cycle?

Three causes of cancer are smoking, radiation, and viruses. They mutate the DNA which causes the cell cycle to not make correct proteins to regulate the cycle. They cannot perform apoptosis.

What is G0?

The G0 phase is when cells do not reproduce or instead pause their cycle between the M and S phases. This can happen in nerve and liver cells.

What are the phases of mitosis? What occurs in each of these phases?

The phases of mitosis are prophase, prometaphase, metaphase, anaphase, telophase, and cytokinesis. In prophase, the chromosomes condense from the chromatin and the nuclear envelope breaks down. In prometaphase, the spindles attach to the chromosomes. In metaphase, the chromosomes align in the center of the cell. In anaphase, the chromosomes separate into sister chromatids and line up on either side of the cell. In telophase, the nuclear envelope reforms, and the chromosomes decondense into chromatin. In cytokinesis, the cell splits into two daughter cells.

What would happen if there was a mutation in the receptor protein? How would this affect the response of the cell?

This could cause a mis-folding of the protein which may lead to no response from a cell, or it may lead to increased binding of a ligand. a. It may inhibit a response because the ligand couldn't bond, or it would increase the response.

Where is the receptor for a protein hormone?

the plasma membrane of the cell

Where is the receptor for a steroid hormone?

nucleus of the cell