Question 1

Which of the following best describes the sequence of events leading to the release of intracellular calcium following activation of a Gq protein-coupled receptor?

Accepted Answer

Ligand binds receptor → Gq protein activates phospholipase C → PIP2 is cleaved into IP3 and DAG → IP3 binds ER receptor → calcium released

Question 2

What is the primary function of diacylglycerol (DAG) produced during Gq protein signaling?

Accepted Answer

To activate protein kinase C (PKC) at the plasma membrane

Question 3

Which equation correctly represents the cleavage of PIP2 by phospholipase C?

Accepted Answer

$$\mathrm{$$PIP_2$$} \xrightarrow{PLC} \mathrm{IP_3$} + \mathrm{DAG}$$

Question 4

A mutation prevents the dissociation of the Gq alpha subunit from the beta-gamma complex. What is the most likely cellular consequence?

Accepted Answer

Phospholipase C will not be activated, so IP3 and DAG will not be produced.

Question 5

Which of the following is a direct effect of IP3 binding to its receptor on the endoplasmic reticulum?

Accepted Answer

Opening of ligand-gated calcium channels, allowing $$\mathrm{Ca$$^{2+}$$} to $$flow into the cytosol

Question 6

Which of the following best explains why calcium must be tightly regulated within the cell?

Accepted Answer

Unregulated calcium leads to continuous activation of calcium-dependent proteins, disrupting normal cell function and potentially causing cell death.

Question 7

Which messenger is responsible for activating smooth muscle contraction via Gq protein-coupled receptors, as shown in the table?

Accepted Answer

Acetylcholine

Question 8

What is the role of calmodulin in calcium signaling?

Accepted Answer

It binds $$\mathrm{Ca$$^{2+}$$}$$, changes conformation, and activates target proteins such as kinases and phosphatases.

Question 9

Which of the following scenarios would most likely result from the use of a calcium ionophore such as ionomycin in a cell?

Accepted Answer

Calcium would be released from intracellular stores regardless of receptor activation.

Question 10

During fertilization, what is the significance of the calcium wave observed in the egg cell?

Accepted Answer

It triggers activation of the egg and initiates embryonic development.

Question 11

Which of the following best describes the function of protein kinase C (PKC) in the context of Gq signaling?

Accepted Answer

PKC is activated by DAG and calcium, leading to phosphorylation of target proteins that regulate cell growth, secretion, and cytoskeletal changes.

Question 12

A researcher uses a fluorescent calcium indicator to study signaling in neurons. What property of the indicator allows it to measure calcium levels?

Accepted Answer

It changes fluorescence intensity in response to binding $$\mathrm{Ca$$^{2+}$$}.$$

Question 13

Which of the following is NOT a function regulated by intracellular calcium signaling?

Accepted Answer

Synthesis of glucose from fatty acids

Question 14

If a cell's ER calcium ATPase is inhibited, what is the most likely outcome?

Accepted Answer

Cytosolic calcium levels will remain elevated, disrupting cellular functions.

Question 15

Which of the following best explains why IP3 is considered a 'second messenger'?

Accepted Answer

It relays signals from the cell surface to intracellular targets, amplifying the response to extracellular signals.

Question 16

Which of the following is a correct statement about the Gq protein subunits?

Accepted Answer

The alpha subunit dissociates upon GTP binding and activates phospholipase C.

Question 17

Which regulated function is correctly paired with its messenger, according to the table?

Accepted Answer

Glycogen degradation – Antidiuretic hormone

Question 18

A drug that blocks IP3 receptors on the ER would most likely have which effect?

Accepted Answer

Prevent calcium release from the ER in response to extracellular signals

Question 19

Which of the following best describes the role of calmodulin after binding calcium?

Accepted Answer

It undergoes a conformational change and activates target proteins such as kinases.

Question 20

Which process is most directly affected if DAG is not produced during Gq signaling?

Accepted Answer

Activation of protein kinase C (PKC)

Signal Transduction via Gq Proteins, IP3/DAG Pathway, and Calcium Regulation in Cells

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