Q: Which equation correctly represents the conversion of ATP to cAMP by adenylyl cyclase in a GPCR signaling cascade?

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

Question 1

Which of the following best describes the function of ligand-gated ion channels in neurons?

Accepted Answer

They directly convert extracellular signals into changes in membrane potential by allowing ions to flow across the membrane.

Question 2

A patient is exposed to muscarine, a compound that acts as an agonist for muscarinic acetylcholine receptors. What is the expected effect on cardiac muscle cells?

Accepted Answer

Decrease in heart rate due to reduced cAMP and increased efflux of positive ions.

Question 3

Which equation correctly represents the conversion of ATP to cAMP by adenylyl cyclase in a GPCR signaling cascade?

Accepted Answer

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

Question 4

Which of the following is TRUE regarding the context-dependent effects of adrenaline on different cell types?

Accepted Answer

Adrenaline increases heart contraction rate, stimulates glucose release in the liver, and increases glucose consumption in muscles.

Question 5

Which of the following statements about GPCRs (G protein coupled receptors) is correct?

Accepted Answer

GPCRs have 7 transmembrane domains and activate intracellular signaling cascades without forming direct ion channels.

Question 6

A neuron is at its resting membrane potential. Which of the following changes will make it more likely to fire an action potential?

Accepted Answer

Influx of $$\mathrm{Na^+}$$ ions, making the inside of the cell less negative.

Question 7

Which of the following best explains why activating nicotinic and muscarinic acetylcholine receptors produces different physiological effects?

Accepted Answer

Nicotinic receptors are ligand-gated ion channels, while muscarinic receptors are GPCRs, leading to distinct signaling mechanisms.

Question 8

Which of the following is a correct sequence of events at a chemical synapse?

Accepted Answer

Electrical signal in presynaptic neuron → vesicle release of neurotransmitter → neurotransmitter binds postsynaptic receptor → postsynaptic response

Question 9

Which of the following cell types is NOT typically considered electrically active and does NOT commonly express postsynaptic receptors?

Accepted Answer

Red blood cells

Question 10

A researcher applies nicotine to a muscle cell. Which receptor is activated and what is the expected effect?

Accepted Answer

Nicotinic acetylcholine receptor; increased influx of $$\mathrm{Na^+}$$ ions and muscle contraction.

Question 11

Which of the following best describes the role of second messengers in GPCR signaling?

Accepted Answer

They amplify the signal from the receptor and activate downstream effectors such as ion channels.

Question 12

Which of the following equations correctly represents the breakdown of cAMP by phosphodiesterase?

Accepted Answer

$$\mathrm{cAMP} \xrightarrow{	ext{phosphodiesterase}} \mathrm{AMP}$$

Question 13

Which of the following is a key difference between ionotropic and metabotropic receptors?

Accepted Answer

Ionotropic receptors directly mediate ion flow, while metabotropic receptors activate intracellular signaling cascades.

Question 14

Which of the following scenarios would make a neuron less likely to fire?

Accepted Answer

Opening of chloride channels, allowing $$\mathrm{Cl^-}$$ ions to enter the cell.

Question 15

Which of the following best explains the opposing effects of adrenaline and acetylcholine on the heart?

Accepted Answer

Adrenaline activates GPCRs that increase cAMP and heart rate, while acetylcholine activates GPCRs that decrease cAMP and slow heart rate.

Question 16

Which of the following is NOT a major family of signaling protein receptors discussed in the study materials?

Accepted Answer

Voltage-gated calcium receptors

Question 17

A mutation causes a GPCR to be constitutively active in liver cells. What is a likely consequence?

Accepted Answer

Increased breakdown of energy stores and excessive release of glucose into the bloodstream.

Question 18

Which of the following best describes the role of the presynaptic neuron at a synapse?

Accepted Answer

It releases neurotransmitters in response to an electrical signal.

Question 19

Which of the following is a real-world example of a ligand-gated ion channel and its physiological effect?

Accepted Answer

Nicotinic acetylcholine receptor in skeletal muscle; allows rapid muscle contraction in response to nerve stimulation.

Cell Signaling and Communication: Receptors and Synaptic Transmission

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