Q: Which of the following equations correctly represents the conversion of ATP to cyclic AMP (cAMP) by adenylyl cyclase?

$$\mathrm{ATP} \xrightarrow{\text{adenylyl cyclase}} \mathrm{cAMP} + \mathrm{PP_i}$$

Question 1

Which of the following best describes the three stages of cell signaling, as illustrated by the impala's response to a cheetah chase?

Accepted Answer

Reception, transduction, response

Question 2

In the context of cell signaling, what is the primary function of a G protein-coupled receptor (GPCR)?

Accepted Answer

To bind signaling molecules and activate G proteins by exchanging GDP for GTP

Question 3

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

Accepted Answer

Paracrine signaling acts locally, while endocrine signaling involves hormones traveling through the bloodstream to distant cells.

Question 4

Which of the following best explains why steroid hormones can activate intracellular receptors?

Accepted Answer

Steroid hormones are hydrophobic and can diffuse through the plasma membrane.

Question 5

A mutation causes a receptor tyrosine kinase (RTK) to remain permanently active. What is a likely consequence of this mutation?

Accepted Answer

Uncontrolled cell division, potentially leading to cancer

Question 6

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

Accepted Answer

$$\mathrm{ATP} \xrightarrow{	ext{adenylyl cyclase}} \mathrm{cAMP} + \mathrm{PP_i}$$

Question 7

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 8

In the fight-or-flight response, epinephrine triggers the breakdown of glycogen to glucose in muscle cells. Which step in the signaling pathway is responsible for amplifying the signal so that one molecule of epinephrine can result in the production of millions of glucose molecules?

Accepted Answer

Enzyme cascades during signal transduction

Question 9

Which of the following is a function of scaffolding proteins in signal transduction pathways?

Accepted Answer

They increase the efficiency of signal transduction by grouping together relay proteins.

Question 10

Which of the following statements about second messengers is correct?

Accepted Answer

Second messengers are small, nonprotein, water-soluble molecules or ions that relay signals inside the cell.

Question 11

A researcher adds a drug that inhibits phosphodiesterase to a cell. What is the expected effect on cAMP levels in the cell?

Accepted Answer

cAMP levels will increase because cAMP is not being broken down.

Question 12

Which of the following best explains why calcium ions ($$\mathrm{Ca$$^{2+}$$}) $$can function as 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 an example of direct cell-to-cell communication in animals?

Accepted Answer

Gap junctions allowing ions and small molecules to pass between adjacent cells

Question 14

Which of the following is a likely outcome if a cell's protein phosphatases are nonfunctional?

Accepted Answer

Proteins will remain phosphorylated, and signaling pathways may remain active longer than normal.

Question 15

Which of the following best describes the specificity of cell signaling?

Accepted Answer

Different cells have different collections of proteins, so the same signal can produce different responses in different cells.

Question 16

Which of the following is the correct sequence of events for a ligand-gated ion channel receptor?

Accepted Answer

Ligand binds receptor → channel opens → specific ions flow through → cellular response

Question 17

Which of the following best explains why signal transduction pathways often involve multiple steps?

Accepted Answer

Multiple steps allow for amplification, regulation, and integration of the signal.

Question 18

Which of the following is a direct result of the activation of a transcription factor by a signaling pathway?

Accepted Answer

Increased or decreased transcription of specific genes

Question 19

A cell is exposed to a signaling molecule that binds to a receptor tyrosine kinase (RTK). Which of the following events is most likely to occur next?

Accepted Answer

The RTK dimerizes and autophosphorylates, activating multiple relay proteins.

Question 20

Which of the following best describes the termination of a cell signaling response?

Accepted Answer

Inactivation mechanisms return the cell to its normal state when the signal is no longer present.

Cell Communication and Signal Transduction

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