Question 1

Which of the following best describes the role of negative feedback in maintaining homeostasis?

Accepted Answer

It reduces the effect of the stimulus, returning the system to its set point.

Question 2

During childbirth, the pressure of the baby's head against the uterus stimulates contractions, which in turn increase the pressure and stimulate more contractions. What type of feedback loop is this an example of?

Accepted Answer

Positive feedback

Question 3

Which method of cell communication involves the release of chemical messengers that travel through the bloodstream to reach distant target cells?

Accepted Answer

Endocrine signaling

Question 4

A signaling molecule binds to a receptor protein, causing the receptor to change shape. What is this step called in a signal transduction pathway?

Accepted Answer

Reception

Question 5

Which type of membrane receptor is directly involved in allowing ions such as $$\mathrm{Na^+} or$$ $$\mathrm{Ca$$^{2+}$$} to $$enter the cell upon ligand binding?

Accepted Answer

Ion channel receptor

Question 6

In a phosphorylation cascade, which enzymes are responsible for adding phosphate groups to proteins?

Accepted Answer

Kinases

Question 7

Why can $$\mathrm{Ca$$^{2+}$$}$$ act as a powerful secondary messenger in signal transduction pathways?

Accepted Answer

A small change in its cytosolic concentration leads to a large percentage change.

Question 8

Which phase of the cell cycle is characterized by DNA replication?

Accepted Answer

S phase

Question 9

During which stage of mitosis do sister chromatids separate and move toward opposite poles?

Accepted Answer

Anaphase

Question 10

What is the main function of cyclin-dependent kinases (Cdks) in the cell cycle?

Accepted Answer

They activate or inactivate proteins by phosphorylating them, but only when bound to cyclin.

Question 11

A cell is observed to continue dividing even though it has DNA damage and should have stopped at the G1 checkpoint. Which gene is most likely mutated?

Accepted Answer

Tumor suppressor gene

Question 12

Which of the following is true about proto-oncogenes?

Accepted Answer

When mutated, they can lead to uncontrolled cell division.

Question 13

Which external signal is necessary for most animal cells to divide?

Accepted Answer

Anchorage dependence

Question 14

What is the primary difference between benign and malignant tumors?

Accepted Answer

Malignant tumors metastasize, while benign tumors remain localized.

Question 15

Which organelle is responsible for organizing spindle fibers during mitosis?

Accepted Answer

Centrosome

Question 16

A cell receives a signal to divide but fails to pass the G2 checkpoint. What is the most likely reason?

Accepted Answer

DNA was not copied correctly during S phase.

Question 17

Which of the following best explains why scaffolding proteins are important in signal transduction pathways?

Accepted Answer

They increase the efficiency of signal transduction by organizing pathway components.

Question 18

If a ligand detaches from its receptor, what happens to the signal transduction pathway?

Accepted Answer

The signal response is quickly terminated.

Question 19

Which of the following equations best represents the phosphorylation of a protein by a kinase?

Accepted Answer

$$\mathrm{Protein} + \mathrm{ATP} \rightarrow \mathrm{Protein{-}P} + \mathrm{ADP}$$

Question 20

A mutation causes a cell to ignore density-dependent inhibition and continue dividing even when crowded. Which process is most directly affected?

Accepted Answer

Cell cycle regulation

Cell Communication, Signal Transduction, and the Cell Cycle

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