Question 1

Which of the following best describes quorum sensing in bacteria?

Accepted Answer

A process where bacteria communicate to sense local population density using signaling molecules.

Question 2

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 another protein, triggering multiple signal transduction pathways.

Question 3

Which of the following is a key difference between local and long-distance signaling in animals?

Accepted Answer

Local signaling involves direct contact or short-range molecules, while long-distance signaling uses hormones transported via the circulatory system.

Question 4

Which of the following best explains why the cholera toxin is deadly?

Accepted Answer

It modifies a G protein so that it is stuck in its active form, causing continuous production of cAMP and massive water loss from intestinal cells.

Question 5

Which of the following is NOT a typical function of scaffolding proteins in signal transduction?

Accepted Answer

They degrade signaling molecules to terminate the signal.

Question 6

A mutation causes a cell to produce a nonfunctional protein phosphatase. What is the most likely consequence?

Accepted Answer

The cell will have difficulty turning off signal transduction pathways, leading to prolonged or inappropriate responses.

Question 7

Which of the following statements about second messengers is correct?

Accepted Answer

Second messengers are small, nonprotein, water-soluble molecules or ions that spread throughout a cell by diffusion.

Question 8

Which of the following best describes the role of protein kinases in a phosphorylation cascade?

Accepted Answer

They transfer phosphate groups from ATP to proteins, activating or deactivating them.

Question 9

A steroid hormone enters a target cell and binds to its receptor. What is the most likely immediate result?

Accepted Answer

The hormone-receptor complex acts as a transcription factor, turning specific genes on or off.

Question 10

Which of the following is an example of paracrine signaling?

Accepted Answer

A growth factor released by one cell stimulates nearby cells to divide.

Question 11

Which of the following is a direct result of ligand binding to a ligand-gated ion channel receptor?

Accepted Answer

The receptor changes shape, opening a channel that allows specific ions to flow through.

Question 12

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

Accepted Answer

Their cytosolic concentration is normally much lower than outside the cell, so small changes have large effects.

Question 13

Which of the following is a likely outcome if a cell lacks functional G protein-coupled receptors (GPCRs)?

Accepted Answer

The cell will be unable to respond to many water-soluble signaling molecules.

Question 14

Which of the following is a real-life example of apoptosis in human development?

Accepted Answer

The removal of cells between developing fingers and toes to form separate digits.

Question 15

Which of the following best describes the role of caspases in apoptosis?

Accepted Answer

They are proteases that cut up proteins and DNA during programmed cell death.

Question 16

A cell receives a signal that activates a G protein, which then activates adenylyl cyclase. What is the next step in this signaling pathway?

Accepted Answer

Adenylyl cyclase converts ATP to cyclic AMP ($$cAMP$$), which acts as a second messenger.

Question 17

Which of the following is a reason why the same signal can produce different responses in different cell types?

Accepted Answer

Different cells have different collections of proteins and signaling pathways.

Question 18

Which of the following is an example of signal amplification in a cell signaling pathway?

Accepted Answer

A single activated receptor leads to the activation of many molecules of a downstream protein.

Question 19

Which of the following is a possible consequence of defective apoptosis in human cells?

Accepted Answer

Increased risk of cancer due to failure to eliminate damaged or abnormal cells.

Cell Communication: Chapter 11 Study Notes (Campbell Biology, 12th Edition)

Guida di studio - Domande di pratica