ap bio unit 4 test

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

18 percent

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

25 percent

Cancer can result from a variety of different mutational events. Which of the following is LEAST likely to result in the initiation of a cancerous tumor?

A defect in a cell-cycle checkpoint prevents a cell from entering the S phase.

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.

(a) Describe the role of mitosis in the growth of a plant. (b) Explain why there are more cells observed in mitosis in the root tip than in the woody stem. (c) Refine the model in the space provided for your response by using the letters from four of the cell labels of Sample 2 to represent the sequential steps of mitosis.

A) Mitosis helps the plant grow by creating genetically identical daughter cells. More cells means more plant growth. B) The root tip shows more cells undergoing mitosis because the root tip needs to grow more than the woody stem. Thus, the root tip cells divide more frequently. It's like how some parts of the human body like muscles and the brain never divide, but skin cells are frequently dividing. C) E, D, B, C

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.

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 statements best explains Delta's role in regulating cell communication through the Notch signaling pathway?

Delta restricts cell communication to short distances within a developing embryo.

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.

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.

Which of the following best describes the physiological response to an overall increase in cellular respiration in the body?

In response to low blood pH, the pH sensors send a signal to the brain, which then sends a signal to the diaphragm, resulting in an increased rate of breathing to help eliminate excess blood CO 2 .

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.

Which of the following statements best describes the role of cyclic AMP in the signal transduction pathway?

It acts as a second messenger that helps relay and amplify the signal within the cell.

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.

Ethylene causes fruits to ripen. In a signaling pathway, receptors activate transcription factors, which ultimately leads to ripening. 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.

Describe and discuss the role of a receptor located in the cell membrane with respect to cellular communication.

Membrane receptors are specialized protein molecules attached to or integrated into the cell membrane. Through interaction with specific ligands (e.g., hormones and neurotransmitters), the receptors facilitate communication between the cell and the extracellular environment.

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.

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, decreasing 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.

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.

Most cells that have become transformed into cancer cells have which of the following characteristics when compared to normal, healthy cells?

Shorter cell cycle

Cell communication is critical for the function of both unicellular and multicellular eukaryotes. Which of the following is likely true of cell signaling?

Similar cell signaling pathways in diverse eukaryotes are evidence of conserved evolutionary processes.

The figure above represents a generalized hormone-signaling pathway. Briefly explain the role of each numbered step in regulating target gene expression.

Step 1 = hormone/ligand binding to receptor to initiate/trigger/induce signaling OR signal reception Step 2 = an intracellular cascade that transduces/amplifies/transfers the signal from plasma membrane to nucleus (or other cellular effectors) Step 3 = transcription/expression of target genes is stimulated/repressed

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

Describe the phases of the cell cycle.

The cell cycle is composed of interphase (G₁, S, and G₂ phases), followed by the mitotic phase (mitosis and cytokinesis), and G₀ phase. Interphase consists of where the cell increases in size (G1 stage), copies its DNA (S stage), prepares to divide (G2 stage), and divides in mitosis. Mitosis is made up of prophase, metaphase, anaphase, and telophase.

Describe how the cell cycle is regulated and discuss ONE consequence of abnormal regulation.

The cell cycle is regulated by checkpoints, which block cell cycle progress unless specific molecular and/or physical conditions are satisfied. One abnormal regulation could be the continuous division of cancer cells. Cancer cells do not require a signaling for division to proceed.

Which of the following conditions will most likely cause a normal body cell to become a cancer cell?

The environment contains mutagens that induce mutations that affect cell-cycle regulator proteins.

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 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.

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 describes a primary function of plasmodesmata?

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

Which of the following will most likely result from a loss of p53 function?

Uncontrolled cell proliferation

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

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