Question 1

Which of the following best describes the process of quorum sensing in bacteria?

Accepted Answer

Bacteria sense local population density by detecting the concentration of signaling molecules.

Question 2

In yeast mating, what is the primary function of the secreted 'a' and 'α' factors?

Accepted Answer

To locate and recognize cells of the opposite mating type for fusion.

Question 3

Which of the following is a key difference between paracrine and endocrine signaling?

Accepted Answer

Endocrine signaling involves long-distance communication, while paracrine signaling is local.

Question 4

A cell responds to a hormone only if it has a receptor specific to that hormone. This concept is best described as:

Accepted Answer

Signal specificity

Question 5

Which of the following is NOT a function of receptor tyrosine kinases (RTKs)?

Accepted Answer

Acting as a gate for ion channels

Question 6

What is the role of protein kinases in signal transduction pathways?

Accepted Answer

They transfer phosphates from ATP to proteins, activating them.

Question 7

Which equation correctly represents the conversion of ATP to cyclic AMP (cAMP) by adenylyl cyclase?

Accepted Answer

$$\mathrm{ATP} \rightarrow \mathrm{cAMP} + \mathrm{PP_i}$$

Question 8

A mutation causes a G protein to remain active, continuously stimulating adenylyl cyclase. What is the most likely cellular consequence?

Accepted Answer

Continuous production of cAMP, leading to excessive cellular responses

Question 9

Which of the following best explains why calcium ions ($$\mathrm{Ca$$^{2+}$$}) $$are effective second messengers?

Accepted Answer

A small change in their number causes a large percentage change in cytosolic concentration.

Question 10

Which of the following is a correct sequence for the three stages of cell signaling?

Accepted Answer

Reception → Transduction → Response

Question 11

A steroid hormone enters a cell and binds to an intracellular receptor. What is the most likely outcome?

Accepted Answer

Formation of a hormone-receptor complex that acts as a transcription factor

Question 12

Which of the following best describes the function of scaffolding proteins in cell signaling?

Accepted Answer

They increase signal transduction efficiency by grouping relay proteins together.

Question 13

In the context of apoptosis, what is the role of caspase proteins?

Accepted Answer

They promote programmed cell death by chopping up cellular components.

Question 14

Which of the following is a real-world example of signal amplification in a cell?

Accepted Answer

A single epinephrine molecule binding to a receptor leads to the production of $$10^8$$ molecules of glucose-1-phosphate.

Question 15

Which of the following statements about ligand-gated ion channel receptors is correct?

Accepted Answer

They open to allow specific ions to pass through the membrane when a ligand binds.

Question 16

Which of the following best describes the molecular switch mechanism in signal transduction?

Accepted Answer

Protein kinases and phosphatases regulate protein activity by phosphorylation and dephosphorylation.

Question 17

Which of the following is a plausible consequence of interference with apoptosis in human cells?

Accepted Answer

Uncontrolled cell growth, potentially contributing to cancer

Question 18

Which of the following is a correct description of the role of second messengers in cell signaling?

Accepted Answer

They are small, nonprotein molecules or ions that spread through the cell by diffusion.

Question 19

Which of the following best explains why the same signaling molecule can produce different responses in different cell types?

Accepted Answer

Different cells have different collections of proteins and pathways.

Question 20

Which of the following is a correct sequence for the phosphorylation cascade in a signal transduction pathway?

Accepted Answer

Protein kinase 1 activates protein kinase 2, which activates protein kinase 3, leading to a cellular response.

Cell Communication and Signal Transduction

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