Question 1

Which of the following best explains why the bacterial potassium channel selectively allows $$\mathrm{K^+}$$ ions to pass but not $$\mathrm{Na^+}$$ ions, despite $$\mathrm{Na^+}$$ being smaller?

Accepted Answer

The channel's selectivity filter forms optimal interactions with the larger $$\mathrm{K^+}$$ ion, allowing it to shed its hydration shell, while $$\mathrm{Na^+}$$ cannot form these interactions and remains hydrated.

Question 2

A hydropathy plot is used to predict membrane-spanning regions of a protein. What feature on the plot indicates a likely transmembrane alpha-helix?

Accepted Answer

A region with a high positive hydropathy index, typically spanning about 20 amino acids.

Question 3

Which of the following is an example of secondary active transport?

Accepted Answer

The sodium-glucose symporter, which uses the $$\mathrm{Na^+}$$ gradient to drive glucose uptake.

Question 4

Which equation correctly describes the free energy change ($$\Delta G) $$for the transport of an ion across a membrane?

Accepted Answer

$$\Delta G = RT \ln \left( \frac{[C]_2}{[C]_1} \right) + zF\Delta \Psi$$

Question 5

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

Accepted Answer

GPCRs activate heterotrimeric G proteins by promoting the exchange of GDP for GTP on the alpha subunit.

Question 6

Which of the following best describes the difference between primary and secondary active transport?

Accepted Answer

Primary active transport uses ATP hydrolysis directly, while secondary active transport uses the energy stored in an ion gradient.

Question 7

A mutation in the $$\mathrm{Na^+/K^+}$$ ATPase prevents it from hydrolyzing ATP. What is the most likely consequence for the cell?

Accepted Answer

The cell will lose its membrane potential due to the inability to maintain $$\mathrm{Na^+}$$ and $$\mathrm{K^+}$$ gradients.

Question 8

Which of the following is a key feature of receptor tyrosine kinases (RTKs) in signal transduction?

Accepted Answer

Ligand binding induces dimerization and autophosphorylation of the receptor.

Question 9

Which of the following best describes antiport membrane transporters?

Accepted Answer

They transport two different molecules in opposite directions across the membrane.

Question 10

A neuron is depolarized when $$\mathrm{Na^+}$$ channels open. What is the primary reason for this depolarization?

Accepted Answer

$$\mathrm{Na^+}$$ ions flow into the cell, making the inside more positive.

Question 11

Which of the following is NOT a component of the electrochemical gradient for an ion?

Accepted Answer

The temperature of the cell.

Question 12

Which of the following best describes facilitated diffusion?

Accepted Answer

Transport of molecules down their concentration gradient via a membrane protein, without energy input.

Question 13

Which of the following is a second messenger commonly produced in GPCR signaling pathways?

Accepted Answer

cAMP

Question 14

Which of the following statements about membrane-associated proteins is TRUE?

Accepted Answer

Peripheral membrane proteins are loosely associated with the membrane and can be removed by changes in pH or ionic strength.

Question 15

Which of the following best explains how the $$\mathrm{Na^+/K^+}$$ ATPase contributes to the resting membrane potential?

Accepted Answer

It pumps 3 $$\mathrm{Na^+}$$ ions out and 2 $$\mathrm{K^+}$$ ions in per ATP hydrolyzed, creating a net negative charge inside the cell.

Question 16

Which of the following is a correct sequence of events in GPCR signaling?

Accepted Answer

Ligand binds GPCR → G protein activated → Adenylyl cyclase activated → cAMP produced

Question 17

Which of the following is a common mechanism for terminating GPCR signaling?

Accepted Answer

Hydrolysis of GTP to GDP on the G protein alpha subunit.

Question 18

Which of the following best describes the function of a symporter?

Accepted Answer

It transports two different molecules in the same direction across the membrane.

Question 19

A patient has a mutation that causes their voltage-gated $$\mathrm{Na^+}$$ channels to remain open longer than normal. What is a likely effect on their neurons?

Accepted Answer

Prolonged depolarization, leading to increased neuronal excitability.

Question 20

Which of the following is TRUE regarding the thermodynamics of membrane transport?

Accepted Answer

Transport of an uncharged molecule down its concentration gradient is spontaneous if $$[C]_2 \u003c [C]_1$$ and $$\Delta G \u003c 0.$$

Membrane Transport and Biosignaling Study Notes

Guida di studio - Domande di pratica

Study guide - Flashcard