Question 1

Which of the following best describes the role of a ligand in cell signaling?

Accepted Answer

A ligand is a chemical signal secreted by a cell that binds to a receptor on a target cell to initiate a response.

Question 2

What is the primary function of phosphorylation in a signal transduction pathway?

Accepted Answer

Phosphorylation adds a phosphate group to a protein, which can activate or deactivate the protein.

Question 3

Which of the following is an example of cell-to-cell contact signaling?

Accepted Answer

A signaling molecule binding to a receptor protein on an adjacent cell membrane.

Question 4

Gap junctions in animal cells and plasmodesmata in plant cells both serve what function?

Accepted Answer

They allow for the direct transfer of signaling molecules between adjacent cells.

Question 5

A hydrophilic ligand binds to its receptor on the cell membrane. What is the next step in the signal transduction pathway?

Accepted Answer

The receptor undergoes a conformational change, transmitting the signal into the cell.

Question 6

Which of the following best explains why only certain cells respond to a particular signaling molecule?

Accepted Answer

Only cells with the correct receptor protein for the ligand can respond to the signal.

Question 7

In the DNA damage pathway, what is the role of p53?

Accepted Answer

p53 inhibits the cell cycle, preventing the division of damaged cells.

Question 8

What would happen to the concentration of intermediate B if enzyme 3 in a metabolic pathway is inhibited?

Accepted Answer

Intermediate B would build up because it cannot be converted to C.

Question 9

Which of the following is a correct statement about negative feedback in biological systems?

Accepted Answer

Negative feedback slows down or stops a response to maintain homeostasis.

Question 10

A mutation changes the shape of a receptor protein involved in a signaling pathway. What is the most likely outcome?

Accepted Answer

The pathway may be disrupted, preventing the cell from responding to the signal.

Question 11

Which of the following best describes the role of a second messenger in a signal transduction pathway?

Accepted Answer

A second messenger is a small molecule that relays and amplifies the signal inside the cell.

Question 12

Which of the following is an example of positive feedback?

Accepted Answer

Blood clotting, where the response amplifies the original stimulus.

Question 13

Botulinum toxin (Botox) causes paralysis by interfering with which part of the signaling pathway?

Accepted Answer

It breaks down SNARE proteins, preventing neurotransmitter release.

Question 14

Which of the following equations best represents the process of phosphorylation?

Accepted Answer

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

Question 15

Which of the following is NOT a possible cellular response to a signal transduction pathway?

Accepted Answer

Destruction of the plasma membrane.

Question 16

A cell releases a signaling molecule that affects only nearby cells. This is an example of:

Accepted Answer

Paracrine signaling.

Question 17

Which of the following best explains why positive feedback is less common than negative feedback in maintaining homeostasis?

Accepted Answer

Positive feedback usually leads to uncontrolled responses, while negative feedback stabilizes physiological processes.

Question 18

Which of the following is true about G protein-coupled receptors (GPCRs)?

Accepted Answer

GPCRs are activated when a ligand binds, causing the G protein to phosphorylate and activate a second messenger.

Question 19

If a mutation prevents the production of a second messenger in a signal transduction pathway, what is the most likely result?

Accepted Answer

The signal will not be relayed to the nucleus, and the cellular response will not occur.

Cell Signaling and Communication Lesson 5.6

Study Guide - Practice Questions