AP Biology Unit 4 Practice Test & Exam | 26 Questions

Questions 1-3 refer to the following diagrams of cell signaling.

1. Which of the following correctly identifies the type of signaling shown in Diagram Y?

(A)Endocrine signaling(B)Paracrine signaling(C)Direct contact signaling(D)Synaptic signaling

2. Which of the following best explains a key difference between the signaling shown in Diagram Z and the signaling in Diagrams X and Y?

(A)The signal in Diagram Z is a protein, while the signals in X and Y are lipids.(B)The target cells in Diagram Z are not specific, while they are highly specific in X and Y.(C)The signal in Diagram Z travels over long distances via the circulatory system, while the signals in X and Y act locally.(D)The signaling molecule in Diagram Z enters the target cell, while the molecules in X and Y bind to surface receptors.

3. A researcher discovers that a particular signaling molecule is found in both simple yeast and complex mammals. The molecule is used in pathways that regulate cell growth. What does the presence of this molecule in such diverse organisms suggest?

(A)The molecule is a recent evolutionary adaptation for multicellularity.(B)All organisms require the same signals for cell growth.(C)Signaling pathways that use this molecule evolved early in the history of life and are highly conserved.(D)Mammals inherited this signaling molecule directly from yeast through horizontal gene transfer.

Questions 4-6 refer to the following model of a signal transduction pathway.

4. Based on the model, what is the primary role of cAMP in this pathway?

(A)It acts as the initial ligand that binds to the receptor.(B)It functions as a second messenger that relays the signal from the membrane to the cytoplasm.(C)It serves as an enzyme that directly converts ATP into a cellular response.(D)It is a G protein that activates adenylyl cyclase.

5. Which step in the pathway represents the transduction of the signal?

(A)The ligand binding to the GPCR.(B)The cellular response triggered by the phosphorylation of target proteins.(C)The series of events from the activation of the G protein to the activation of Protein Kinase A.(D)The release of the signaling molecule from the original cell.

6. A certain toxin prevents G proteins from hydrolyzing GTP to GDP. How would this toxin most likely affect the signaling pathway?

(A)The pathway would be blocked at the reception stage, as the ligand could no longer bind.(B)The G protein would remain in its active state, continuously stimulating adenylyl cyclase and leading to an overproduction of cAMP.(C)The G protein would be unable to bind to the GPCR, preventing any signal from being relayed.(D)The pathway would be inhibited because Protein Kinase A would not be activated.

7. During childbirth, the hormone oxytocin stimulates uterine contractions. These contractions, in turn, stimulate the release of more oxytocin from the pituitary gland. This cycle continues until the baby is delivered. This process is an example of:

(A)a negative feedback loop, because it eventually stops.(B)a positive feedback loop, because the response amplifies the original stimulus.(C)homeostasis, because it maintains a stable state in the mother's body.(D)signal termination, because the pathway is turned off by the final product.

8. Apoptosis, or programmed cell death, is a crucial process in development and tissue maintenance. Which of the following describes a key role of signal transduction in apoptosis?

(A)Apoptosis is triggered by a single type of external signal that blocks all cell division.(B)Signal transduction pathways can be initiated by internal or external signals that activate a cascade of "suicide" proteins.(C)Apoptosis occurs when negative feedback loops in the cell cycle fail, leading to uncontrolled cell death.(D)The signals for apoptosis always originate from neighboring cells to eliminate damaged tissue.

Questions 9-11 refer to the following graph showing the relative concentration of different molecules during the eukaryotic cell cycle.

9. What does the graph indicate about the concentration of CDK during the cell cycle?

(A)It peaks during the S phase when DNA is replicated.(B)It is synthesized and degraded in a cyclical manner.(C)It remains relatively constant throughout all phases.(D)It is highest during the G1 phase to prepare for division.

10. Based on the data and your knowledge of cell cycle regulation, which of the following best explains the relationship between cyclin and CDK?

(A)The active CDK-cyclin complex triggers the cell to progress through checkpoints, and the degradation of cyclin deactivates the complex.(B)The concentration of CDK determines the concentration of cyclin.(C)Cyclin phosphorylates CDK to activate it, allowing the cell to enter mitosis.(D)CDK acts as a receptor for cyclin, which is an external growth factor.

11. A researcher observes that in a certain type of cancer cell, the specific cyclin shown in the graph is not degraded at the end of M phase. Which of the following claims is best supported by this evidence?

(A)The cell will be arrested in G1 phase.(B)The cell will be unable to replicate its DNA in S phase.(C)The cell will exit the cell cycle and enter G0.(D)The cell will continue to divide uncontrollably because the CDK-cyclin complex remains active.

12. A cell in the G2 phase of the cell cycle has 20 chromatids. How many chromosomes will each daughter cell have after mitosis and cytokinesis are complete?

(A)5(B)10(C)20(D)40

13. Which of the following correctly describes the events of anaphase in mitosis?

(A)Chromosomes condense and the nuclear envelope breaks down.(B)Chromosomes align at the metaphase plate.(C)Sister chromatids separate and are pulled to opposite poles of the cell.(D)The nuclear envelope re-forms and chromosomes decondense.

14. If a person’s blood sugar level rises after a meal, the pancreas releases insulin, which causes cells to take up glucose. This lowers the blood sugar level. Which of the following claims best describes this regulatory process?

(A)It is a positive feedback mechanism because insulin is released in response to a stimulus.(B)It is a negative feedback mechanism because the response (lower blood sugar) counteracts the initial stimulus (high blood sugar).(C)It is a form of local signaling, as insulin only affects cells near the pancreas.(D)It is an example of a phosphorylation cascade that always leads to gene expression.

15. Many medications work by interfering with normal signal transduction pathways. A class of drugs called beta-blockers binds to beta-adrenergic receptors but does not activate them, preventing the hormone epinephrine from binding. This is an example of a chemical that:

(A)activates a signaling pathway by acting as a ligand.(B)inhibits a signaling pathway by blocking the receptor.(C)acts as a second messenger to amplify a signal.(D)alters gene expression by binding directly to DNA.

Questions 16-18 refer to the following information and diagram.

16. Based on the data, which of the following claims is best supported?

(A)Mitosis is the longest phase of the cell cycle.(B)Interphase is the longest phase of the cell cycle.(C)Anaphase is the longest phase of mitosis.(D)Cytokinesis occurs immediately after prophase.

17. Using the data, what is the approximate duration of metaphase in these cells?

(A)12 minutes(B)72 minutes(C)120 minutes(D)180 minutes

18. A scientist treats a sample of onion root tip cells with a chemical that inhibits the formation of the mitotic spindle. Which of the following provides the best reasoning for why the cell cycle would be arrested at the M checkpoint?

(A)The M checkpoint verifies that DNA has been replicated correctly, and the chemical damages DNA.(B)The M checkpoint ensures that all chromosomes are properly attached to the spindle fibers before anaphase begins.(C)The M checkpoint assesses whether the cell is large enough to divide, and the chemical shrinks the cell.(D)The M checkpoint is regulated by external growth factors, which are blocked by the chemical.

19. Quorum sensing is a process used by bacteria to coordinate group behaviors based on population density. Individual bacteria produce and release signaling molecules. Once the concentration of these molecules reaches a critical threshold, it triggers a collective response, such as forming a biofilm. This is a form of:

(A)long-distance endocrine signaling.(B)cell communication that allows unicellular organisms to act like a multicellular unit.(C)direct cell-to-cell contact through gap junctions.(D)a negative feedback loop to limit population growth.

20. A mutation in the gene for a receptor protein results in a change in the shape of its ligand-binding site. Which of the following is the most likely consequence of this mutation?

(A)The receptor will now be able to bind to many different types of ligands.(B)The original ligand will not be able to bind to the receptor, preventing the initiation of the signaling pathway.(C)The signal transduction pathway will be permanently activated, even in the absence of the ligand.(D)The receptor will move from the cell surface into the cytoplasm.

21. Cancer is often characterized by uncontrolled cell division. This condition is most likely a result of:

(A)disruptions in the regulation of the cell cycle.(B)the activation of apoptosis pathways.(C)a failure of cells to enter the S phase.(D)an overly active negative feedback loop.

22. A key feature of many signal transduction pathways is the amplification of the signal. Which of the following best explains how a phosphorylation cascade contributes to signal amplification?

(A)Each receptor molecule can only activate one protein kinase molecule.(B)Each activated protein kinase can phosphorylate and activate many other kinase molecules, creating an expanding cascade.(C)The original signaling molecule is replicated at each step of the cascade.(D)Second messengers like cAMP are degraded quickly, which amplifies the signal.

23. A cell is observed to have condensed chromosomes, a fragmented nuclear envelope, and a mitotic spindle forming. Which of the following is the most reasonable claim about the stage of the cell cycle this cell is in?

(A)The cell is in anaphase.(B)The cell is in G1 of interphase.(C)The cell is in prophase.(D)The cell is in telophase.

24. The p53 protein is a tumor suppressor that can halt the cell cycle at the G1/S checkpoint if it detects DNA damage. It can also trigger apoptosis if the damage is irreparable. A mutation that results in a nonfunctional p53 protein is a common feature of cancer cells. Which of the following provides the best reasoning for this observation?

(A)Without functional p53, the cell cannot synthesize cyclins, so it gets stuck in G1.(B)Without functional p53, the cell cannot properly replicate its DNA during S phase.(C)Without functional p53, damaged DNA can be replicated, leading to the accumulation of mutations that promote uncontrolled division.(D)Without functional p53, the cell undergoes apoptosis too frequently, leading to tissue damage.

AP Biology Unit 4: Cell Communication and Cell Cycle Practice Exam

Exam Details

A. Multiple-Choice Questions (24 Questions)

B. Short Answer Questions (2 Questions)

AP Biology Unit 4: Cell Communication and Cell Cycle Practice Exam

Exam Details

A. Multiple-Choice Questions (24 Questions)

B. Short Answer Questions (2 Questions)