Unit 4 Test AP Classroom Questions

Which statement provides the evidence to justify the claim that signal transduction may result in an altered phenotype?

If the SRY gene is absent or nonfunctional, the embryo will exhibit female sexual development.

Which of the following statements accurately uses the information presented to support the hypothesis that interruption of M function in a single body cell can result in cancer?

Growth-factor signaling can trigger mitosis in cells that are in direct contact with other cells.

What is the expected percent change in the DNA content of a typical eukaryotic cell as it progresses through the cell cycle from the start of the G1 phase to the end of the G2 phase?

+100%

Based on the data, the percent of the mitotic cells that were in metaphase is closest to which of the following?

18%

Based on Table 1, what percent of the life cycle of yeast cells is spent in DNA replication?

25 percent

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

Which of the following steps in a signaling pathway typically occurs first once a chemical messenger reaches a target cell?

A ligand binds to a receptor.

The graph above shows changes in glucagon and insulin secretions at different concentrations of blood glucose. Which of the following feedback mechanisms is best supported by the data?

A low glucose level causes the release of glucagon, which stimulates the release of more glucose from tissues, which in turn lowers the amount of glucagon being released.

In mammals, an increase in the concentration of sodium in the blood triggers the release of antidiuretic hormone (ADH) from the pituitary gland. As the concentration of sodium in the blood returns to previous levels, the release of ADH from the pituitary gland is reduced. Based on the information presented, which of the following describes the most likely role of ADH in maintaining blood osmolarity?

ADH promotes an increase in the movement of water into the bloodstream.

Damaged tissue releases chemicals that activate platelets and stimulate the formation of blood clots. Which of the following predictions about the activity of platelets best describes a positive feedback mechanism?

Activated platelets release chemicals that activate more platelets.

Which of the following statements best justifies the claim that changes in the expression of ced−9 in C. elegans can affect regulation of apoptosis in the cell?

An experiment showed that a mutation in the ced−9 gene led to excessive cell death in C. elegans.

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?

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

Based on the model presented, which of the following statements expresses the proper relationship between osmolarity, ADH release, and urine production?

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

Warfarin is a drug used to treat certain blood clots. Warfarin blocks the formation of the active form of vitamin K-dependent clotting factors. Based on the model, which of the following best predicts the effects of warfarin on a patient?

Factor X will not be activated, which will prevent thrombin from forming.

A researcher claims that the epinephrine signaling pathway controls a catabolic process in muscle cells. Which of the following statements best helps justify the researcher's claim?

Glycogen phosphorylase catalyzes the conversion of glycogen to glucose-1-phosphate.

The model shown in the figure represents the role of two hormones, calcitonin and parathyroid hormone (PTH), in maintaining normal blood calcium levels in humans. If a dietary change results in an increase in blood calcium concentration above normal levels, which of the following is the most likely effect on calcium homeostasis?

Calcitonin levels will rise, thus promoting the deposit of calcium into bones.

Which of the following justifies the claim that differences in components of cell signaling pathways explain the different responses to epinephrine?

Cell signaling depends on the ability to detect a signal molecule. Not all cells have receptors for epinephrine. Only cells with such receptors are capable of responding.

Which of the following best explains the role of cell-to-cell communication during a response to an invasion of antigens?

Chemicals that are secreted from antigen-presenting cells then activate helper T cells.

Which of the following presents a correct interpretation of the changes in chromosome number depicted in Figure 1?

Chromosomes enter metaphase containing two chromatids attached by a centromere. During anaphase, the chromatids are separated, each becoming a chromosome. Cytokinesis distributes the chromosomes into two separate cells.

Based on the model, which of the following best explains how regulation of neurotransmitter release might increase the range of responses to a stimulus in the nervous system?

Different neurons in the same neural network can release different amounts of neurotransmitter.

Based on Figure 1, which of the following best explains how exercise causes blood glucose levels to rise?

Epinephrine activates alpha cells, causing the release of glucagon, and inhibits beta cells, blocking the release of insulin.

Which of the following best predicts what will happen to the blood glucose level if the person has another meal at 5 p.m.?

Immediately after the meal, the blood glucose level will increase, and then insulin will be secreted to counter the increase.

Based on Figure 1, which of the following statements best describes the epinephrine signaling pathway?

In involves enzymes activating other enzymes.

Which of the following best predicts the effect of a mutation that causes EGFR to be active in the absence of a growth factor?

Increased cell division will lead to the formation of a tumor.

Cortisol is a hormone produced in response to stress, including starvation, in humans. Which of the following is most likely an immediate effect of a starvation-induced increase in cortisol secretion?

Increased mobilization of fatty acids from fat cells

Which of the following statements best describes the role of adenylyl cyclase in the epinephrine signaling pathway?

It accelerates the production of a second messenger.

Which of the following best describes the component that metformin represents in a signal transduction pathway that regulates glucose production in the liver?

It is a ligand that activates the signal transduction pathway of the activation of AMPK

Which of the following best supports the claim that ethylene initiates the signal transduction pathway that leads to ripening of fruit?

Loss-of-function mutations in ethylene receptors result in changes to the ripening process.

Based on the sample means, which of the following conclusions about the cells in the growing root tips of Zea mays seedlings is best supported by the results of the experiment?

More cells are produced per unit of time in the root tips growing in compact sand than in the root tips growing in loose sand.

Air is less dense at very high elevations, so less oxygen is available than in the denser air at sea level. Based on the model in Figure 1, if a person travels from sea level to a high elevation location, which of the following correctly predicts the response to the decreased blood oxygen level?

More erythropoietin will be secreted from the kidneys, increasing production of erythrocytes.

A researcher found a mutation that resulted in the PFK enzyme being unable to bind ATP to the allosteric site. Which of the following best predicts the effect of the mutation?

Negative feedback regulation does not occur, so the enzyme will be active when glycolysis is not needed.

A researcher examining a root tip observes a plant cell with condensed sister chromatids, kinetochores with attached microtubules, and individual chromosomes that are aligned at the equatorial plate of the cell. Which of the following best describes what the next process will be in the cell?

Paired chromatids will separate, and the new daughter chromosomes will move toward opposite poles of the cell.

During mitosis, which of the following normally occurs?

Replicated chromosomes line up on the equatorial plate.

Which of the following most accurately describes an observation and an effect of the viral infection indicated by the data in Table 1?

Seventy-five percent of the virus-infected cells are found in mitosis. The virus stimulates frequent cell division.

In flowering plants, plasmodesmata are narrow channels through cell walls that connect the cytoplasms of adjacent cells. An explanation of how plant cells communicate across cell walls will most likely refer to the diffusion through plasmodesmata of which of the following?

Small, water-soluble molecules

Based on Figure 1, which of the following statements correctly links a stage of the cell cycle with the event occurring at that stage?

Synthesis of sufficient DNA for two daughter cells occurs in stage II.

Which of the following best explains how treatment with a drug that stimulates the production of insulin receptors on target cells will affect the insulin signaling pathway in an individual with type 1 diabetes?

The drug will have little or no effect on the signaling pathway because the receptors will not be activated in the absence of insulin.

Which of the following best explains a possible mechanism that would enable the hormone to efficiently reach all of the target cells in the body?

The hormone is released into the bloodstream where it can be transported to all cells with the correct receptors.

Which of the following outcomes will most likely result from the irreversible binding of GDP to the G protein?

The intracellular concentration of glycogen will increase.

Which of the following changes in the FGFR signaling pathway is most likely to result in uncontrolled cell proliferation?

The irreversible association of FGFR proteins

Which of the following is represented by the gradual increase in thickness of the arrows from the top to the bottom of Figure 1 ?

The number of signaling molecules that are produced or activated increases with each step in the pathway.

Vertebrate immune responses involve communication over short and long distances. Which of the following statements best helps explain how cell surface proteins, such as MHC proteins and T cell receptors, mediate cell communication over short distances?

The proteins interact directly with proteins on the surfaces of other cells.

Which of the following outcomes will most likely result from the inactivation of the beta-2 adrenergic receptor?

The rate of glycogen synthesis in the cell will increase.

Which of the following statements best predicts the effect of a loss of function of the insulin receptor's intracellular domain?

The storage of GLUT4 in vesicles inside the cell will increase.

Trypsinogen is split by the enzyme enterokinase to form an activated molecule of the protease trypsin. Which of the following would confirm that the activation of trypsin is an example of how a positive feedback mechanism can amplify a biological process?

The trypsin produced by the reaction is capable of splitting and activating additional trypsinogen molecules.

Which statement best predicts why a cell's progression through the cell cycle might be halted at the G1/S checkpoint?

There are not enough nucleotides available to construct new DNA

Which of the following statements is consistent with the data in Figure 1?

There is a change from 3 to 6 picograms of DNA because DNA is replicated before each round of cell division.

Which of the following statements best explains a primary function of plasmodesmata?

They allow the movement of molecules from one cell to another, enabling communication between cells.

The tumor suppressor protein p53 binds to DNA and activates target genes, which results in the synthesis of p21, CD95, and other proteins. The p21 protein promotes cell-cycle arrest, whereas the CD95 protein promotes apoptosis. Which of the following will most likely result from a loss of p53 function?

Uncontrolled cell proliferation

Which of the following describes the critical role of cAMP during the transduction stage of a GG protein signal transduction pathway?

cAMP results in the activation of an enzyme that amplifies the signal by acting on many substrate molecules.

DNA replication occurs

during the S phase of the cell cycle