AP Biology : Understanding the Cell Cycle

Study concepts, example questions & explanations for AP Biology

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Example Questions

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Example Question #31 : Understanding The Cell Cycle

Which of these is/are point(s) at which the cell cycle is controlled?

I. G1/S

II. S/M

III. G1 

IV. G2/M

V. Telophase and cytokinesis

Possible Answers:

I and IV

III and V

I, II, III, IV, and V

IV only

III only

Correct answer:

I and IV

Explanation:

The two major checkpoints that control the cell cell are the transition between G1/S and G2/M phases of the cell cycle. The G1/S checkpoint will monitor DNA damage prior to the cell entering the S phase for replication. Following replication during S phase, the G2/M checkpoint ensures DNA replication happened correctly. At both these checkpoints, the cell will slow down until any problems detected by the checkpoints are resolved so that the cell does not replicate defective cells. Without these checkpoints, mutations and disease processes such as cancer can occur and these diseased cells may replicate freely. There is also another checkpoint in the M phase that will ensure that the spindle fibers are correctly formed and the chromosomes are correctly aligned along the metaphase plate in order for anaphase to follow normally.

Example Question #32 : Understanding The Cell Cycle

The regulatory subunit of maturation-promoting factor __________.

Possible Answers:

removes a phosphate group from certain tyrosine residues of specific protein substrates

transfers a phosphate group to certain serine and threonine residues of specific protein substrates

converts ADP to ATP

converts ATP to ADP

is called cyclin because its concentration rises and falls predictably as the cell cycle progresses

Correct answer:

is called cyclin because its concentration rises and falls predictably as the cell cycle progresses

Explanation:

Cyclin controls the progression since cyclin-dependent kinases (CDK's) are inactive unless bound to cyclins, this is what controls the cell cycle progression. The cyclin levels in the cell will control the activity of CDK's. If they are bound, the CDK's are then phosphorylated by distinct kinases, which leads to their activation and subsequent downstream effects. Cyclins do not directly remove a phosphate from ATP to ADP. They also do not directly phosphorylate anything in the answer choices, they specially bind the CDK and that process regulates if the cell cycle is up or down regulated in the cell.

Example Question #33 : Understanding The Cell Cycle

Which of the following does not regulate cyclin-dependent kinases (CDK's) to influence a cell's progress through the cell cycle?

I. Cyclin concentration

II. CDK phosphorylation/unphosphorylation

III. Subcellular localization

IV. Controlled cell lysis

Possible Answers:

IV only

I, II, III, and IV

I, II, and III

II only

I and II

Correct answer:

IV only

Explanation:

Cell lysis is not regulated by cyclin-dependent kinases (CDK). Cyclin concentration, CDK phosphorylation/unphosphorylation, and subcellular localization all influence a cell's progress through the cell cycle. The main control of the cell cycle speed and regulation is cyclin concentration, which is responsible for regulating CDK activity. CDK is inactive if cyclin concentration is low, and is active if cyclin concentration is high. Also, CDK control phosphorylation/unphosphorylation depending on its activity level based on cyclin concentration, this process also control the cell cycle progression. Lastly, subcellular localization controls concentration by sequestering cyclin/CDK complexes in different locations to control concentration levels that affect cell cycle progression.

Example Question #34 : Understanding The Cell Cycle

__________ are surveillance mechanisms that halt the progress of the cell cycle if any of the various events involved not working correctly or are not happening in the correct order.

Possible Answers:

Activation energies

Allosteric inhibitors

Monitors

Checkpoints

Chaperones

Correct answer:

Checkpoints

Explanation:

Checkpoints are what monitor and control the process of the cell cycle and lower incidence of problems with cell growth and replication. The major three checkpoints in the cell cycle are the checkpoint before the S phase at the end of G1 phase to check for DNA damage. The second checkpoint is in the G2 phase before the M phase. The third major checkpoint in the cell cycle in at the end of M phase before anaphase occurs. Checkpoints are the points of control in the cell cycle regulation that are regulated by cyclin dependent kinases and cyclin levels; each checkpoint has its unique cyclins.

Example Question #35 : Understanding The Cell Cycle

Which of the following is a trait unique to cancer cells?

Possible Answers:

They do not undergo interphase

They communicate with other cells through chemical signalling

Density-dependent growth factors limit their division

They have escaped form cell cycle controls and inhibitions

They do not use glucose as an energy source

Correct answer:

They have escaped form cell cycle controls and inhibitions

Explanation:

Cancer cells are not controlled by cyclins and cyclin-dependent kinases, which regulate the cell cycle. They would not proceed through interphase if the system of checkpoints was still in place. The system of chemical signaling is mostly destroyed, preventing the cancer cells from being controlled by surrounding normal cells. Cancer cells, like virtually all body cells, utilize glucose for energy.

Example Question #36 : Understanding The Cell Cycle

What is the correct order of the cell cycle?

Possible Answers:

G1, G2, S, M

G1, S, G2, M

S, G1, G2, M

G1, S, M, G2

G1, G2, M, S

Correct answer:

G1, S, G2, M

Explanation:

G1 (gap 1 phase) is the first stage of the cell cycle. Growth and some preparation for cell division occurs in this stage. If the cell is not preparing to divide then it enters the G0 stage (gap 0 phase): the resting gap stage where neither growth nor division occurs. The S stage (DNA Synthesis phase) comes next and there chromosome duplication occurs. G2 (gap phase 2) is after the S stage and there cell growth continues and everything is checked to make sure the cell can divide. Finally, M stage (mitotic stage) is last and there mitosis occurs and two new daughter cells begin the cell cycle again. Keep in mind that at the end of each stage there are "checkpoints" that the cell needs to pass in order to keep going forward. Cancer occurs when a cell bypasses those checkpoints and continues to replicate without those controls.

Example Question #37 : Understanding The Cell Cycle

When does chromosome duplication occur?

Possible Answers:

Prophase

G0 Stage

Interphase

Prometaphase

Metaphase 

Correct answer:

Interphase

Explanation:

It is important to note that chromosome duplication happens before mitosis, so interphase is correct. More specifically, it happens in the S stage of interphase.Cell cycle

Example Question #38 : Understanding The Cell Cycle

In which of the following cell cycle phases does DNA replication occur?

Possible Answers:

G1 phase

G2 phase

M Phase

G0 phase

S phase

Correct answer:

S phase

Explanation:

The "S" phase, known as the synthesis phase, is the portion of the cell cycle where DNA is replicated. The other stages listed do not contain DNA replication. G0 is a cell cycle arrest phase, where a cell remains dormant, awaiting signals to re-enter the cell cycle.

Example Question #39 : Understanding The Cell Cycle

Which of the following terms is used to describe programmed cell death?

Possible Answers:

Apoptosis

Procaspases

Anaphase

Caspases

Necrosis

Correct answer:

Apoptosis

Explanation:

Caspases are proteases that initiate apoptosis. Procaspases are inactive caspases that are stored in the cell. Necrosis is when the cell body dies due to cell injury. Apoptosis is programmed cell death. The cell uses it to control the rate of cell division. Anaphase is a phase in the cell cycle in which the chromosomes are pulled to opposite poles of the cell.

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