Unit 2 Progress Check: MCQ, AP Biology | Unit 4 MCQ Practice Questions

Testosterone is a small steroid hormone that is important in cell signaling. Which of the following indicates where testosterone enters a cell and why it is able to cross at that point?

A - 1, because testosterone is nonpolar and can diffuse through the membrane. Steroids such as testosterone are hydrophobic lipids. Therefore, testosterone can cross the hydrophobic inner region of the phospholipid bilayer.

A magnesium sulfate solution taken orally can cause a net movement of water into the large intestine, which results from water molecules diffusing through aquaporins embedded in the cells of the intestinal lining. By which of the following mechanisms do the water molecules most likely move into the large intestine?

A - By passive transport from an area of low osmolarity to an area of high osmolarity. Based on the information presented, the water molecules move through aquaporins by diffusing from an area of low osmolarity to an area of high osmolarity, which is an example of passive transport.

Aldosterone (a steroid hormone) is a small, nonpolar, hydrophobic molecule that enters a target cell by moving across the plasma membrane, down a concentration gradient. Based on the information presented, how does aldosterone most likely enter target cells?

A - By simple diffusion. Small, nonpolar, hydrophobic molecules can enter a cell by moving across the plasma membrane and down a concentration gradient by simple diffusion.

Intravenous (IV) therapy is used for fluid replacement in instances of dehydration in humans and other animals. One type of IV fluid is essentially a saltwater solution. To determine the best concentration for therapy in people, a team of students is researching the effects of solutions of different salt concentrations on red blood cells. The following observations were made from three different red blood cell samples viewed under a microscope. The team wants to extend the research project. Wha

A - Repeat the process with other salt concentrations. The figures illustrate the extremes of hypotonic (swollen cells) and hypertonic (shriveled cells) environments, so an extension would be to investigate the small range of acceptable salt concentrations in IVIV fluid solutions.

Lysosomes digest food particles brought into a cell by endocytosis. After a vesicle containing food particles fuses with a lysosome, H+ ions are transported into the lysosome from the cytosol. This significantly lowers the pH of the lysosome relative to the cytosol and activates the enzymes that digest the particles. Which of the following best predicts what will happen to the lysosomal enzymes if the proteins that transport H+ ions from the cytosol into the lysosome are damaged?

A - The lysosomal enzymes will not become active, since there will be no active transport of H+H+ ions. Since the pHpH of the lysosome has to become lower than that of the cytosol, active transport is needed to move H+H+ ions into the lysosome, against the H+H+ ion concentration gradient, to activate the enzymes.

Stomata are pores on the surfaces of the leaves and stems of plants that regulate gas exchange between the plants and the atmosphere. Researchers found that the stomata density on the leaves of a species of plant change as the concentration of CO2 in the atmosphere changes. When grown at 350 ppm CO2 the plant has an average density of 300 stomata per mm2, but when grown at 400 ppm CO2 the plant has an average density of 250 stomata per mm2. Which of the following best describes how the ratio of

A - The ratio decreases from 0.860.86 to 0.630.63, because fewer stomata are needed at higher CO2CO2 concentrations. The ratio of 300 stomata per mm2mm2 to 350 ppmppm CO2CO2 is 0.860.86, and the ratio of 250 stomata per mm2mm2 to 400 ppm CO2CO2 is 0.630.63. This reflects that fewer stomata are needed as the concentration of CO2CO2 increases.

Researchers have discovered details about apoptosis (programmed cell death) by studying embryologic development of a nematode worm, Caenorhabditis elegans. Apoptosis is a normal developmental process in C. elegans. They found several genes involved in apoptosis, including ced−9 and ced−3 . The ced−3 gene was found to promote cell death, and ced−9 to inhibit it. The ced−9 gene serves as a regulator that prevents apoptosis in the absence of a signal promoting apoptosis. Which of the fol

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

During a fight-or-flight response, epinephrine is released into the body's circulatory system and transported throughout the body. Some cells exhibit a response to the epinephrine while other cells do not. Which of the following justifies the claim that differences in components of cell signaling pathways explain the different responses to epinephrine? A) Cell signaling depends on the ability to detect a signal molecule. Not all cells have receptors for epinephrine. Only cells with such recept

A) 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.

An antigen can induce an immune response in a host organism. Antigens are targeted by antibodies that are produced by the organism's immune system in response to contact with the antigen. Antibodies are specific to antigens. Many different cell types are involved in immune responses. Which of the following best describes the role of cell-to-cell communication during a response to an invasion of antigens? A) Chemicals that are secreted from antigen-presenting cells then activate helper T cells.

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

Fibroblast growth factor receptors (FGFRs) are transmembrane proteins that regulate cellular processes such as cell proliferation and differentiation. The extracellular domains of FGFR proteins bind specifically to signaling molecules called fibroblast growth factors. The intracellular domains of FGFR proteins function as protein kinases, enzymes that transfer phosphate groups from ATP to protein substrates. FGFR activation occurs when binding by fibroblast growth factors causes FGFR proteins in

A) The irreversible association of FGFR proteins

Adjacent plant cells have narrow channels called plasmodesmata that pass through the cell walls of the connected cells and allow a cytoplasmic connection between the cells. Which of the following statements best describes a primary function of plasmodesmata? A) They allow the movement of molecules from one cell to another, enabling communication between cells. B) They prevent the cell membrane from pulling away from the cell wall during periods of drought. C) They eliminate the need to produce

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

A student is using dialysis bags to model the effects of changing solute concentrations on cells. The student places one dialysis bag that contains 25 mL of distilled water into each of two beakers that are filled with 200 mL of distilled water. (Figure 1). The membrane of each dialysis bag membrane contains pores that allow small solutes such as monoatomic ions to pass through but are too small for anything larger to pass. After 30 minutes, 5 mL of a concentrated solution of albumin (a medium-s

B The graph indicates no change in the mass of the dialysis bag for the first 30 minutes in an isotonic environment and then shows a decrease in mass when the environment became hypertonic with the addition of albumin.

A study was conducted to understand the factors controlling the rate at which molecules or ions travel across cell membranes. An artificial membrane was created that was composed of a phospholipid bilayer only. The speed at which various substances crossed this membrane was measured. Some substances can pass through an actual cell membrane much faster than they passed through the artificial membrane in this study. Which of the following statements best explains this finding?

B - Actual cell membranes have a variety of proteins embedded in the membrane that are absent in the artificial membrane. Actual cell membranes have a variety of embedded proteins that increase the movement of substances across the membrane by both active and passive transport.

Some cells, such as intestinal cells, exchange a lot of material with their surroundings. The surface-to-volume ratio of these cells affects the efficiency of material exchange. Based on the data, which cell is likely to be most effective in the exchange of materials?

B - Cell 2 The surface area to volume calculation is 60/10=6. Of the four cells, this one has the highest ratio of surface area to volume and is likely to be most effective in the exchange of materials.

In an experiment, researchers compared the growth of two different plants, plant X and plant Y. The researchers maintained the plants under nearly identical conditions and observed that plant X grew faster than plant Y. The researchers also observed that the inner mitochondrial membranes of plant X had more folds than did those of plant Y. Which of the following conclusions about increasing the number of folds in the inner mitochondrial membrane is best supported by the results of the experimen

B - It increases the surface area available for ATPATP production, which results in faster cell growth. The increased surface area of the folds will contain more ATPATP synthase, allowing for more efficient use of the chemiosmotic gradient and more efficient production of ATPATP. The observation that plant XX grew faster than plant YY supports this conclusion.

In an experiment, researchers provided a radiolabeled amino acid to living plant cells. After one hour, the researchers determined the amount of the radiolabeled amino acid that was in each of several subcellular compartments. The results of the experiment are represented in the table. Which of the following conclusions about the radiolabeled amino acid is best supported by the results of the experiment?

B - It was mostly incorporated into proteins that regulate and manage metabolic reactions. Amino acids are the building block of proteins, and the data indicate that most of the radiolabeled amino acid was in the mitochondria. Therefore, the data best support the conclusion that most of the amino acid molecules were incorporated into proteins that regulate and manage the metabolic reactions that occur in mitochondria.

The figure shows a representation of a protein embedded in a cell membrane. The numbers indicate different structural regions of the protein. Based on the figure, which of the following statements best describes the relationship between regions 1 and 2 of the protein?

B - Region 1 is hydrophilic because it interacts with an aqueous environment, whereas region 2 is hydrophobic because it interacts with the interior of the membrane. A cell membrane is a phospholipid bilayer that separates one aqueous environment from another. The interior of a phospholipid bilayer is a hydrophobic environment. Because region 1 interacts with the aqueous environment on one side of the phospholipid bilayer, it is most likely hydrophilic. Because region 2 interacts with the interior of the phospholipid bilayer, it is most likely hydrophobic.

Some membrane proteins help maintain the concentrations of ions inside a cell by transporting the ions across the cell's plasma membrane. Other membrane proteins form pores in the plasma membrane through which the ions can diffuse. A model showing the influence of membrane proteins on the movement of sodium (Na+) and potassium (K+) ions across a plasma membrane is presented in Figure 1. Based on the model presented in Figure 1, which of the following changes will most likely result from a deple

B - The Na+ concentration inside the cell will increase. Without ATPATP, the Na+ ions will continue to leak into the cell but will not be pumped out of the cell, resulting in a concentration increase inside the cell.

A scientist is studying the various prokaryotic and eukaryotic species found floating in a sample of water taken from a marine ecosystem. Which cellular component will be found in the widest range of organisms in the sample?

B - The ribosome, since all organisms need to synthesize proteins. Ribosomes are found in all forms of life, allowing for comparison of the widest possible range of plankton species.

Beetroot cells contain a family of dark red pigments called betalains. The selectively permeable nature of the beetroot cells keeps the internal environment of the cell separate from the external environment of the cell. Researchers are interested in determining whether the selective permeability of beetroot cells is due to the cell membrane or if it is due to the cell wall. Exposure to cellulase is known to damage the structure of the cell wall. An experiment is set up in which beetroot cells a

B - When beetroot cells are placed in a solution with cellulase, the solution remains clear. Cellulase digests cellulose and damages the structure of the cell wall, not the cell membrane. The lack of color change in the solution indicates that the betalain is not leaking out of the beetroot cells even though the cell wall has been damaged. This refutes the alternative hypothesis.

Signal transduction may result in changes in gene expression and cell function, which may alter phenotype in an embryo. An example is the expression of the SRY gene, which triggers the male sexual development pathway in mammals. This gene is found on the Y chromosome. Which statement provides the evidence to justify the claim that signal transduction may result in an altered phenotype? A) If the SRY gene is absent or nonfunctional, the embryo will exhibit male sexual development. B) If the SRY

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

A person's blood glucose level fluctuates during the day, as represented in Figure 1. Two hormones, insulin and glucagon, are directly involved in regulating the blood glucose level to maintain a healthy level. Insulin acts to lower the blood glucose level, and glucagon acts to increase the blood glucose level. Which of the following best predicts what will happen to the blood glucose level if the person has another meal at 5 p.m.? A) Immediately after the meal, the blood glucose level will de

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

The epidermal growth factor receptor EGFR is a cell surface receptor. When a growth factor binds to EGFR, the receptor is activated. The activated EGFR triggers a signal transduction pathway, which leads to increased frequency of cell division. Which of the following best predicts the effect of a mutation that causes EGFR to be active in the absence of a growth factor? A) Increased apoptosis will lead to abnormal growth of the tissue. B) Increased cell division will lead to the formation of a

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

Metformin is a drug used to treat type 2 diabetes by decreasing glucose production in the liver. AMP-activated protein kinase (AMPK) is a major cellular regulator of glucose metabolism. Metformin activates AMPK in liver cells but cannot cross the plasma membrane. By blocking AMPK with an inhibitor, researchers found that AMPK activation is required for metformin to produce an inhibitory effect on glucose production by liver cells. Which of the following best describes the component that metform

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

Phosphofructokinase (PFK) is a key enzyme in glycolysis. ATP is one of the two substrates for the reaction catalyzed by PFK. ATP is also an allosteric regulator of PFK. Figure 1 shows the enzyme-substrate interactions of PFK. 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? A) The activity of the enzyme will not be affected because the active site is not involved in su

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

The relative amounts of DNA present in the nucleus of a cell at four different stages of the life cycle are shown in Figure 1. Based on Figure 1, which of the following statements correctly links a stage of the cell cycle with the event occurring at that stage? A) Stage I represents the G2 phase of the cell cycle. B) Synthesis of sufficient DNA for two daughter cells occurs in stage II. C) Stage III includes mitosis. D) The replication of genetic material occurs in stage IV.

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

The insulin receptor is a transmembrane protein that plays a role in the regulation of glucose homeostasis. The receptor's extracellular domain binds specifically to the peptide hormone insulin. The receptor's intracellular domain interacts with cellular factors. The binding of insulin to the receptor stimulates a signal transduction pathway that results in the subcellular translocation of GLUT4, a glucose transport protein that is stored in vesicles inside the cell. A simplified model of the in

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

Which statement best predicts why a cell's progression through the cell cycle might be halted at the G1/S checkpoint? A) Spindle fibers have not correctly attached to chromosomes. B) There are not enough nucleotides available to construct new DNA. C) Damage occurred to DNA when it was being copied in G1G1. D) Proteins necessary for M phase of the cell cycle have not been produced.

B) There are not enough nucleotides available to construct new DNA.

The cell membrane is selectively permeable due to its structure. Thus, the internal environment of the cell is distinct from the external environment of the cell. One biologist hypothesizes that small nonpolar molecules readily pass through the membrane. Another biologist alternatively hypothesizes that these types of molecules require channel and transport proteins that are embedded in the membrane in order to move across the membrane. Which of the following data would best refute this alterna

C - CO2CO2 and N2N2 movement in and out of cells is unaffected when membrane protein activity is blocked. Both CO2CO2 and N2N2 are small nonpolar molecules. Their ability to enter and leave cells normally when membrane protein activity is blocked would refute the alternative hypothesis.

Some viral infections can lead to the rupture of the lysosome membrane. Which prediction of the effect of this disruption of cellular compartmentalization is most likely correct?

C - Hydrolytic enzymes will be released, which will cause cell death. Hydrolytic enzymes will be released, resulting in cell death and preventing further viral reproduction.

Researchers investigate the transport of a certain protein into cells by endocytosis. In an experiment, the researchers incubate the cells in the presence of the protein and measure the amount of the protein that is absorbed into the cells over a five-minute period. Based on their observations, what should the researchers do to further clarify how the availability of the protein outside the cells affects the rate of endocytosis of the protein?

C - Incubate the cells in the presence of several different concentrations of the protein. Changing the concentration of the protein will change the availability of the protein outside the cells.

Gaucher disease is an inherited disorder in which cells of the body are unable to break down a particular type of lipid, resulting in a buildup of the lipid in some tissues and organs. Based on the information provided, Gaucher disease results most directly from a defect in the function of which of the following organelles?

C - The lysosome The lysosome contains specific enzymes used to break down a variety of molecules and cellular waste products. A defect in the function of the lysosomal enzymes that are needed to break down lipids is the most direct cause of Gaucher disease.

Hereditary spherocytosis (HS) is a disorder of red blood cells that causes the cells to be smaller and spherical instead of having the usual flattened, biconcave shape. The average diameter of normal red blood cells is 7.2μm, and the average diameter of red blood cells in a person with HS was found to be 6.7μm. The normal red blood cell has an average surface area of 136μm2 and an average volume of 91μm3. Which of the following provides an accurate calculation of the surface area to volume

C - The ratio is 0.890.89, and the cells are less efficient at transferring oxygen. The correct calculation of the surface area to volume ratio of the HSHS cell is 0.890.89. This ratio is less than the ratio found in a normal red blood cell, 1.491.49, so the cell would be less efficient at transferring oxygen.

Which of the following transport mechanisms will be affected most directly by a temporary shortage of ATP molecules inside the cell?

C - The transport of glucose molecules against a concentration gradient. The active transport of glucose molecules against a concentration gradient requires an input of energy. Biological processes that require an input of energy typically incorporate the hydrolysis of ATPATP, an energy-rich molecule.

A student used microscopy to investigate the relative lengths of the different stages of mitosis. The student prepared slides of cells isolated from a growing onion root tip and viewed the slides under a dissecting microscope. The student then made diagrams of cells that were in different stages of mitosis and counted the number of cells that were in each of those stages. The student's data are presented in Table 1. Table 1. Number of cells in each of four different stages of mitosis: Metaphas

C) 18%

A model of the typical life cycle of a cell is shown in Figure 1. Scientists have estimated that it takes yeast cells approximately 20 hours to complete the entire cycle. Table 1 shows the amount of time in each phase of the life cycle for yeast cells. Table 1. Amount of time spent in each stage of the cell cycle by yeast cells: Stage M G1 S G2 Time (hours) 2 10 5 3 Based on Table 1, what percent of the life cycle of yeast cells is spent in DNA replication? A) 5 percent B) 10 percent C) 25 p

C) 25 percent

Which of the following steps in a signaling pathway typically occurs first once a chemical messenger reaches a target cell? A) Specific genes are activated. B) A second messenger molecule is produced. C) A ligand binds to a receptor. D) Specific proteins are synthesized.

C) A ligand binds to a receptor.

A hydrophilic peptide hormone is produced in the anterior pituitary gland located at the base of the brain. The hormone targets specific cells in many parts of the body. 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? A) The hormone interacts with the nerves at the base of the brain and directs signals to the target cells through the nervous system. B) The hormone diffuses into target cells adjace

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

Researchers tracked the amount of DNA (measured in picograms) over time beginning with a single cell and continuing through several rounds of cell division. The researchers observed threadlike chromosomes prior to cell division. The threadlike chromosomes disappeared from view shortly after each division. The amount of DNA in picograms per cell over several rounds of cell division is shown in Figure 1. Which of the following statements is consistent with the data in Figure 1? A) The cells have

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

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? A) Rapid cell growth without cell division B) Immediate activation of apoptosis pathways C) Uncontrolled cell proliferation D) Increased expression of p53 target genes

C) Uncontrolled cell proliferation

Cholesterol is a naturally occurring substance that helps regulate the fluidity of a cell's plasma membrane. A cholesterol molecule can be represented as having a polar head and a nonpolar region, as shown in the figure. Which of the following models shows how cholesterol molecules most likely interact with the phospholipid bilayer of a cell's plasma membrane?

D The model correctly shows the polar heads of the cholesterol molecules interacting with the polar heads of the phospholipids. Also, the model correctly shows the nonpolar regions of the cholesterol molecules interacting with the hydrophobic interior of the phospholipid bilayer.

Researchers have proposed a model of chloroplast evolution. According to the model, chloroplasts evolved from a small prokaryotic organism that was engulfed by an ancestral eukaryote. The engulfed prokaryote then formed an endosymbiotic relationship with the eukaryotic host. Which of the following observations best supports the model?

D - Chloroplasts and some prokaryotes share similar photosynthetic reactions. Photosynthesis is a feature of only a limited number of organisms, including cyanobacteria, algae, and plants. The fact that this specialized process is similar in prokaryotes, such as cyanobacteria, and in eukaryotes, such as algae and plants, provides evidence in support of the model.

Euglenids are single-cell eukaryotes that live in aquatic environments. The chloroplasts found inside euglenids are enveloped by three membranes, as represented in Figure 1. The inner membrane of euglenid chloroplasts resembles the thylakoid membrane. Which of the following claims about the origin of the euglenid chloroplast is best supported by the three-membrane structure of the envelope?

D - It originated from the incorporation of a photosynthetic prokaryote into a eukaryotic cell by two endosymbiotic events. The three-membrane structure of the chloroplast envelope best supports the claim presented in this answer choice. The three-membrane structure most likely resulted from two endosymbiotic events, with the middle membrane originating from the first event and the outer membrane originating from the second event.

Which of the following observations best supports the claim that mitochondria evolved from once-free-living prokaryotic cells by the process of endocytosis?

D - Mitochondria are surrounded by a double membrane. The double membranes of mitochondria provide evidence that an ancestor of mitochondria, which was most likely a type of free-living aerobic bacterium, was ingested via endocystosis by a primitive eukaryotic cell.

A group of mutations, known as MT-ND1, have been identified in mitochondrial DNA. These mutations are associated with a number of debilitating diseases stemming from the production of nonfunctional proteins in the mitochondria. Which of the following cellular deficiencies would most likely be related to these MT-ND1 mutations?

D - The cell is unable to complete reactions related to electron transport and ATP production. The electron transport chain and ATPATP production are associated with proteins in the inner membrane of the mitochondrion. Nonfunctional proteins in the mitochondrion are likely to result in reduced ATP production.

Two competing hypotheses exist regarding the cell membrane structure. One hypothesis states that membrane structure is static and membrane components throughout the bilayer are rigidly bound. Alternatively, the other hypothesis states that cell membranes are a fluid mosaic in which membrane components may drift within the bilayer around the surface of the cell. An experiment is set up in which membrane proteins of two different cells are fluorescently labeled with two different colors and then f

D - The membrane proteins from each cell have mixed and drifted within the bilayer, which supports the fluid mosaic model of cell membranes. Cell membranes consist of a structural framework of phospholipid molecules that is embedded with proteins and steroids that may flow around the surface of the cell within the bilayer.

Researchers conducted an experiment to investigate the effects of a valinomycin treatment on skeletal muscle cells. Valinomycin is a naturally occurring substance that can be used as a drug. The results of the experiment are presented in the table. Which of the following claims about the effects of the valinomycin treatment is best supported by the data presented in the table?

D - The valinomycin treatment caused a decrease in the activity of the mitochondria. The data indicate that the valinomycin treatment caused a decrease in the relative rate of ATPATP production, which likely resulted from impaired mitochondrial function.

Certain bacteria can use both ethyl alcohol and acetate as sources of nutrients. In an experiment where both nutrients are available to a bacterial population, the following results were obtained and graphed. What additional procedure would best help determine whether these movements are due to active transport or to passive transport?

D - Use two additional treatments, one containing only ethyl alcohol and one containing only acetate. Include a substance known to block ATPATP use by the plasma membrane. Compare the graphs of these two treatments to the original graph. Active transport requires the availability of ATPATP. If the nutrients are actively transported, blocking ATPATP use should reduce the rate of transport along the whole concentration range. If these two graphs are the same as the original graph, the transport is passive. Separation of the nutrients eliminates the possibility that the two transport processes could interfere with each other.

Blood clots are formed by a positive feedback loop. Two pathways exist, the extrinsic and intrinsic pathways, which converge during clot formation. There are many clotting factors involved, most of which are proteins. Vitamin K is required for the formation of the active form of several of the clotting factors, including Factor X. A simplified model of the blood clotting process is shown in Figure 1. Warfarin is a drug used to treat certain blood clots. Warfarin blocks the formation of the acti

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

Researchers grew seedlings of corn, Zea mays, in loose and compact sand. The researchers measured the amount of time required for the cells in the growing root tips of the seedlings to double in number. The mean cell doubling times for the two groups of seedlings are shown in Figure 1. 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? A) The cells of the root tips grow

D) 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.

A cell culture commonly used in research was selected to study the effect of a specific virus on the timing of cell cycle phases. Two separate cultures were started, one untreated and one inoculated with the virus. Both cultures were incubated under identical conditions. After a period of time, 200 cells from each culture were observed and classified as shown in Table 1. Table 1. Number of normal and infected cells found in three phases of the cell cycle: Phase of Cell Cycle: G0 Untreated Cell

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

The beta-2 adrenergic receptor is a membrane-bound protein that regulates several cellular processes, including the synthesis and breakdown of glycogen. The receptor binds specifically to the hormone epinephrine. The binding of epinephrine to the beta-2 adrenergic receptor triggers a signal transduction cascade that controls glycogen synthesis and breakdown in the cell. A simplified model of the signal transduction cascade is represented in Figure 1. Which of the following outcomes will most li

D) The rate of glycogen synthesis in the cell will increase.

G proteins are a family of receptor proteins that are involved in transmitting signals from outside a cell to inside a cell. When a signaling molecule binds to a G protein, the G protein is activated. The G protein then activates an enzyme that produces a second messenger called cAMP. Which of the following describes a critical role of cAMP during the transduction stage of a G protein signal transduction pathway? A) cAMP carries the signal to the nucleus of the cell and results in new sequence

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

A certain type of specialized cell contains an unusually large amount of rough endoplasmic reticulum (ER). Which of the following functions is this cell type most likely specialized to perform?

The production and secretion of proteins. The cytosolic surface of the rough ER is covered by ribosomes that synthesize proteins that are then transported into the rough ER, then to the Golgi complex, and finally out of the cell.