unit 4 progress check: mcq

AP Biology Scoring Guide

Unit 4 Progress Check: MCQ

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1. An antigen can induce an immune response in a host organism. Antigens are targeted byantibodies that are produced by the organism’s immune system in response to contact with theantigen. Antibodies are specific to antigens. Many different cell types are involved in immuneresponses.Which of the following best describes the role of cell-to-cell communication during a response to aninvasion of antigens?

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

B A macrophage cell engulfs a pathogen in the blood.

CAntigens attaching to receptors on memory B cells stimulate the memory B cells to become plasmacells.

D Antigen-presenting cells engulf antigens at the first exposure.

2. Adjacent plant cells have narrow channels called plasmodesmata that pass through the cell wallsof the connected cells and allow a cytoplasmic connection between the cells.Which of the following statements best describes a primary function of plasmodesmata?

AThey allow the movement of molecules from one cell to another, enabling communication betweencells.

B They prevent the cell membrane from pulling away from the cell wall during periods of drought.

CThey eliminate the need to produce signaling molecules and eliminate the need for cells to havereceptors for signaling molecules.

DThey increase the surface area available for attachment of ribosomes and thus increase proteinsynthesis.

3. A hydrophilic peptide hormone is produced in the anterior pituitary gland located at the base of thebrain. 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 toefficiently reach all of the target cells in the body?




AThe hormone interacts with the nerves at the base of the brain and directs signals to the target cellsthrough the nervous system.

BThe hormone diffuses into target cells adjacent to the anterior pituitary gland, where the hormone isdegraded.

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

DThe hormone moves through cytoplasmic connections between cells until it has reached all cellswith the correct intracellular binding sites.

4. proteins are a family of receptor proteins that are involved in transmitting signals from outside acell to inside a cell. When a signaling molecule binds to a protein, the protein is activated. The

protein then activates an enzyme that produces a second messenger called .Which of the following describes a critical role of during the transduction stage of a protein signal transduction pathway?

A carries the signal to the nucleus of the cell and results in new sequences of nucleotides

being added to the cell’s .

B binds the extracellular signal molecule and carries it to the intracellular target specified by

the signal.

C modifies a specific monomer so that it can be added to an elongating structural

macromolecule.

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

molecules.

5. Metformin is a drug used to treat type 2 diabetes by decreasing glucose production in the liver.-activated protein kinase is a major cellular regulator of glucose metabolism.

Metformin activates in liver cells but cannot cross the plasma membrane. By blocking with an inhibitor, researchers found that 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 metformin represents in a signaltransduction pathway that regulates glucose production in the liver?




A It is a secondary messenger that amplifies a signal through a cascade reaction.

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

CIt is an allosteric regulator that binds to a crucial section of the that makes the enzymesneeded for glucose uptake.

D It is a competitive inhibitor that binds to glucose and prevents it from entering the cell.

6. Which of the following steps in a signaling pathway typically occurs first once a chemicalmessenger 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.

7. During a fight-or-flight response, epinephrine is released into the body’s circulatory system andtransported throughout the body. Some cells exhibit a response to the epinephrine while other cellsdo not.Which of the following justifies the claim that differences in components of cell signaling pathwaysexplain the different responses to epinephrine?




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

BCell signaling depends on the transduction of a received signal by the nervous system. Not all cellsare close enough to a synapse to receive the signal and respond.

C

Cell signaling depends on the signal being able to diffuse through the cell membrane. Epinephrineis incapable of diffusing through some plasma membranes because of the membrane’sphospholipid composition.

DCell signaling requires reception, transduction, and response. All cells can receive epinephrine, allcells respond with a pathway, but only select cells have the proper coding in their to respond.

8. Signal transduction may result in changes in gene expression and cell function, which may alterphenotype in an embryo. An example is the expression of the gene, which triggers the malesexual 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 analtered phenotype?

A If the gene is absent or nonfunctional, the embryo will exhibit male sexual development.

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

C An embryo with a male sex chromosome will always exhibit male sexual development.

D An embryo with two male sex chromosomes will always exhibit male sexual development.

9. Researchers have discovered details about apoptosis (programmed cell death) by studyingembryologic development of a nematode worm, Caenorhabditis elegans. Apoptosis is a normaldevelopmental process in C. elegans. They found several genes involved in apoptosis, including

and . The gene was found to promote cell death, and to inhibit it.The gene serves as a regulator that prevents apoptosis in the absence of a signalpromoting apoptosis.Which of the following statements best justifies the claim that changes in the expression of in C. elegans can affect regulation of apoptosis in the cell?




AAn experiment showed that a mutation in the gene led to excessive cell death in C.elegans.

BAn experiment showed that the gene normally produces a protein that promotes excessivecell death in C. elegans.

C A mutation in will cause to be incorrectly transcribed.

D Apoptosis is dependent on a signal from the gene in C. elegans.

10. The insulin receptor is a transmembrane protein that plays a role in the regulation of glucosehomeostasis. 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 thereceptor stimulates a signal transduction pathway that results in the subcellular translocation of

, a glucose transport protein that is stored in vesicles inside the cell. A simplified model ofthe insulin receptor–signaling pathway is shown in Figure 1.

Figure 1. A simplified model of the insulin receptor–signaling pathwayWhich of the following statements best predicts the effect of a loss of function of the insulinreceptor’s intracellular domain?




A The stimulation of the signal transduction pathway will increase.

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

C The number of molecules in the plasma membrane will increase.

D The concentration of glucose inside the cell will increase.




11. The beta-2 adrenergic receptor is a membrane-bound protein that regulates several cellularprocesses, including the synthesis and breakdown of glycogen. The receptor binds specifically tothe hormone epinephrine. The binding of epinephrine to the beta-2 adrenergic receptor triggers asignal transduction cascade that controls glycogen synthesis and breakdown in the cell. Asimplified model of the signal transduction cascade is represented in Figure 1.

Figure 1. A simplified model of the signal transduction cascade triggered by epinephrine binding tothe beta-2 adrenergic receptorWhich of the following outcomes will most likely result from the inactivation of the beta-2 adrenergicreceptor?

A The cellular concentration of cyclic will increase.

B The enzymatic activity of protein kinase A will increase.

C The activation of glycogen phosphorylase will increase.

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




12. Fibroblast growth factor receptors are transmembrane proteins that regulate cellularprocesses such as cell proliferation and differentiation. The extracellular domains of proteins bind specifically to signaling molecules called fibroblast growth factors. The intracellulardomains of proteins function as protein kinases, enzymes that transfer phosphate groupsfrom to protein substrates.

activation occurs when binding by fibroblast growth factors causes proteins in theplasma membrane to become closely associated with each other. The association of two proteins stimulates protein kinase activity, which triggers the activation of intracellular signalingpathways. A simplified model of activation is represented in Figure 1.

Figure 1. A simplified model of activationWhich of the following changes in the signaling pathway is most likely to result inuncontrolled cell proliferation?

A The irreversible association of proteins

B The loss of the protein kinase function

C A decrease in the intracellular concentration of

D A decrease in the extracellular concentrations of fibroblast growth factors




13. Phosphofructokinase is a key enzyme in glycolysis. is one of the two substrates forthe reaction catalyzed by . is also an allosteric regulator of . Figure 1 shows theenzyme-substrate interactions of .

Figure 1. The enzyme-substrate interactions of A researcher found a mutation that resulted in the enzyme being unable to bind to theallosteric site. Which of the following best predicts the effect of the mutation?

AThe activity of the enzyme will not be affected because the active site is not involved in substratebinding at the allosteric site.

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

CPositive feedback does not occur, and the activity of the enzyme will decrease when glycolysis isneeded.

D The activity of the enzyme will fluctuate independent of the concentration.




14. A person’s blood glucose level fluctuates during the day, as represented in Figure 1. Twohormones, insulin and glucagon, are directly involved in regulating the blood glucose level tomaintain a healthy level. Insulin acts to lower the blood glucose level, and glucagon acts toincrease the blood glucose level.

Figure 1. Blood glucose fluctuations of an individualWhich of the following best predicts what will happen to the blood glucose level if the person hasanother meal at 5 P.M.?

AImmediately after the meal, the blood glucose level will decrease because of the increase inglucagon levels.

BImmediately after the meal, the blood glucose level will increase, and then insulin will be secreted tocounter the increase.

CSeveral hours after the meal, the blood glucose level will increase sharply because of an increase inthe amount of glucagon secreted.

DThe blood glucose level will not change after the 5 P.M. meal because the person has alreadyconsumed two meals and the blood glucose level has been adjusted to a steady-state level.




15. Blood clots are formed by a positive feedback loop. Two pathways exist, the extrinsic and intrinsicpathways, which converge during clot formation. There are many clotting factors involved, most ofwhich are proteins. Vitamin is required for the formation of the active form of several of theclotting factors, including Factor . A simplified model of the blood clotting process is shown inFigure 1.

Figure 1. Simplified model of clotting cascadeWarfarin is a drug used to treat certain blood clots. Warfarin blocks the formation of the active formof vitamin -dependent clotting factors. Based on the model, which of the following best predictsthe effects of warfarin on a patient?

A Fibrinogen will form fibrin, but the clot will not form because Factor will not be synthesized.

B The intrinsic pathway will take over because the clotting factors are part of that pathway.

C Thrombin will be converted to prothrombin because Factor will reverse the reaction.

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




16. A model of the typical life cycle of a cell is shown in Figure 1.

Figure 1. Typical life cycle of a eukaryotic cellScientists have estimated that it takes yeast cells approximately 20 hours to complete the entirecycle. 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

Time (hours) 2 10 5 3

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




A 5 percent

B 10 percent

C 25 percent

D 50 percent




17. Researchers grew seedlings of corn, Zea mays, in loose and compact sand. The researchersmeasured the amount of time required for the cells in the growing root tips of the seedlings todouble in number. The mean cell doubling times for the two groups of seedlings are shown inFigure 1.

Figure 1. Mean cell doubling times for the growing root tips of Zea mays seedlings planted in looseor compact sandBased on the sample means, which of the following conclusions about the cells in the growing roottips of Zea mays seedlings is best supported by the results of the experiment?




AThe cells of the root tips grow to larger sizes when the seedlings are planted in compact sand thanwhen the seedlings are planted in loose sand.

BThe average rate of mitotic cell division is greater for the root tips growing in loose sand than for theroot tips growing in compact sand.

CThe average cell cycle time is greater for the root tips growing in compact sand than for the root tipsgrowing in loose sand.

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

18. The relative amounts of present in the nucleus of a cell at four different stages of the lifecycle are shown in Figure 1.

Figure 1. Relative amounts of present in the nucleus of a cellBased on Figure 1, which of the following statements correctly links a stage of the cell cycle withthe event occurring at that stage?




A Stage represents the phase of the cell cycle.

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

C Stage includes mitosis.

D The replication of genetic material occurs in stage .

19. Researchers tracked the amount of (measured in picograms) over time beginning with asingle cell and continuing through several rounds of cell division. The researchers observedthreadlike chromosomes prior to cell division. The threadlike chromosomes disappeared from viewshortly after each division. The amount of in picograms per cell over several rounds of celldivision is shown in Figure 1.

Figure 1. Amount of in picograms per cell over several rounds of cell divisionWhich of the following statements is consistent with the data in Figure 1?




A The cells have a haploid chromosome number of 3.

B The cells have a diploid chromosome number of 6.

CThere is a change from 3 to 6 picograms of because is replicated before each round ofcell division.

DThere is a change from 6 to 3 picograms of after each cell division because the chromosomeslengthen following cell division.

20. A cell culture commonly used in research was selected to study the effect of a specific virus on thetiming of cell cycle phases. Two separate cultures were started, one untreated and one inoculated withthe virus. Both cultures were incubated under identical conditions. After a period of time, 200 cells fromeach 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 Untreated Cells ( ) Virus-Infected Cells ( )

196 10

Interphase 2 40

Mitosis 2 150

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

ANormal cells spend 98 percent of their time cycling in and out of interphase. The virus reduces thisto 5 percent of the time.

BTwenty percent of the virus-infected cells are in interphase. These cells are no longer part of the cellcycle.

CForty percent of the virus-infected cells are in interphase. These cells are preparing for replication ofgenetic material.

DSeventy-five percent of the virus-infected cells are found in mitosis. The virus stimulates frequentcell division.




21. A student used microscopy to investigate the relative lengths of the different stages of mitosis. Thestudent prepared slides of cells isolated from a growing onion root tip and viewed the slides undera dissecting microscope. The student then made diagrams of cells that were in different stages ofmitosis and counted the number of cells that were in each of those stages. The student’s data arepresented in Table 1.Table 1. Number of cells in each of four different stages of mitosis

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




A

B

C

D

22. The epidermal growth factor receptor is a cell surface receptor. When a growth factor bindsto , the receptor is activated. The activated 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 to be active in theabsence 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 tumor.

C Cells will exit the cell cycle, entering a non-dividing phase.

D Fewer cells will be in any of the stages of mitosis.

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




A Rapid cell growth without cell division

B Immediate activation of apoptosis pathways

C Uncontrolled cell proliferation

D Increased expression of target genes

24. Figure 1 represents the relative time and sequence of the phases of the cell cycle.

Figure 1. Representation of the cell cycle and identification of the / checkpointWhich statement best predicts why a cell’s progression through the cell cycle might be halted at the

/ checkpoint?



Copyright © 2017. The College Board. These materials are part of a College Board program. Use or distribution of these materials online or in print beyondyour school’s participation in the program is prohibited. of 21

A Spindle fibers have not correctly attached to chromosomes.

B There are not enough nucleotides available to construct new .

C Damage occurred to when it was being copied in .

D Proteins necessary for phase of the cell cycle have not been produced.

unit 4 progress check: mcq

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