Question 1

Which of the following best describes quorum sensing in bacteria?

Accepted Answer

A system where bacteria release and detect signaling molecules to assess local population density and coordinate behaviors such as biofilm formation.

Question 2

In the desperate flight of an impala from a cheetah, which sequence correctly represents the stages of cell signaling in muscle cells?

Accepted Answer

Signal reception → Signal transduction → Cellular response

Question 3

Which type of cell signaling involves the release of neurotransmitters in response to an electrical signal?

Accepted Answer

Synaptic signaling

Question 4

What is the primary function of receptor tyrosine kinases (RTKs) in cell signaling?

Accepted Answer

To catalyze the transfer of phosphate groups from ATP to other proteins, triggering multiple signal transduction pathways.

Question 5

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

Accepted Answer

They are the largest family of cell-surface receptors and require GTP to activate G proteins.

Question 6

A mutation prevents the formation of gap junctions in animal cells. Which process would be most directly affected?

Accepted Answer

Direct cytoplasmic communication between adjacent cells

Question 7

Which equation best represents the phosphorylation reaction catalyzed by receptor tyrosine kinases?

Accepted Answer

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

Question 8

Which of the following signaling molecules can readily cross the plasma membrane and bind to intracellular receptors?

Accepted Answer

Steroid hormones

Question 9

A drug blocks the binding of epinephrine to its receptor on muscle cells. What is the most immediate effect?

Accepted Answer

The signal transduction pathway is not activated, so enzymes that release glucose from glycogen remain inactive.

Question 10

Which of the following is a real-world application of interfering with bacterial quorum sensing?

Accepted Answer

Preventing the formation of biofilms to reduce antibiotic resistance.

Question 11

Which statement best explains why only certain cells respond to a particular hormone?

Accepted Answer

Only cells with the specific receptor for that hormone can respond.

Question 12

Which of the following is an example of paracrine signaling?

Accepted Answer

Growth factors released by one cell stimulate nearby cells to divide.

Question 13

What is the role of a ligand in cell signaling?

Accepted Answer

It binds specifically to a receptor protein, initiating a signal transduction pathway.

Question 14

Which of the following best describes the function of a ligand-gated ion channel receptor?

Accepted Answer

It opens or closes in response to ligand binding, allowing specific ions to pass through the membrane.

Question 15

In yeast mating, what is the result of the signal transduction pathway initiated by the binding of mating factors?

Accepted Answer

Fusion of two yeast cells of different mating types to form a new cell.

Question 16

Which of the following is a key similarity between cell signaling in yeast and mammals?

Accepted Answer

Both use highly specific signal transduction pathways initiated by ligand-receptor binding.

Question 17

Which of the following equations represents the activation of a G protein by a GPCR?

Accepted Answer

$$\mathrm{G\ protein{-}GDP} + \mathrm{GTP} \rightarrow \mathrm{G\ protein{-}GTP} + \mathrm{GDP}$$

Question 18

A mutation causes a receptor protein to lose its ability to change shape after ligand binding. What is the most likely consequence?

Accepted Answer

The signal transduction pathway will not be initiated, and the cellular response will not occur.

Question 19

Which of the following best explains why interfering with quorum sensing could be an alternative to antibiotics?

Accepted Answer

It prevents bacteria from coordinating behaviors like toxin secretion and biofilm formation, reducing their ability to cause disease.

Cell Communication: Mechanisms and Evolution in Biology

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