Q: Which equation correctly represents the stoichiometry of the Na extsuperscript{+}-K extsuperscript{+} ATPase reaction?

$$2\mathrm{K}^{+}_{\text{out}} + 3\mathrm{Na}^{+}_{\text{in}} + \mathrm{ATP} + \mathrm{H}_2\mathrm{O} \rightarrow 2\mathrm{K}^{+}_{\text{in}} + 3\mathrm{Na}^{+}_{\text{out}} + \mathrm{ADP} + P_i$$

Question 1

Which of the following statements best explains why lipids are effective for long-term energy storage in organisms?

Accepted Answer

Lipids are highly reduced, so their oxidation yields more ATP per carbon than carbohydrates.

Question 2

A fatty acid with 18 carbons and one cis double bond is most likely to:

Accepted Answer

Increase membrane fluidity compared to a saturated fatty acid of the same length.

Question 3

Which of the following best describes the structure of a triacylglycerol?

Accepted Answer

One glycerol molecule esterified to three fatty acids.

Question 4

Which class of membrane lipids contains a carbohydrate linked to its head group?

Accepted Answer

Glycoglycerolipids

Question 5

What is the main structural difference between sphingolipids and glycerophospholipids?

Accepted Answer

Sphingolipids contain a fatty acid linked to sphingosine via an amide bond, while glycerophospholipids contain fatty acids esterified to glycerol.

Question 6

Cholesterol is considered only weakly amphipathic because:

Accepted Answer

Its only polar group is a single hydroxyl group.

Question 7

Which of the following membrane lipids is the precursor to all steroids?

Accepted Answer

Cholesterol

Question 8

In the fluid mosaic model of biological membranes, which statement is most accurate?

Accepted Answer

Lipids and proteins diffuse freely within the plane of the membrane.

Question 9

Membrane rafts are important because they:

Accepted Answer

Are dynamic domains rich in cholesterol and sphingolipids, involved in cell signaling and protein sorting.

Question 10

Which of the following statements about nonmediated transport across membranes is correct?

Accepted Answer

It is slow and more rapid for hydrophobic solutes than for polar/charged solutes.

Question 11

Facilitated transport differs from active transport in that:

Accepted Answer

Facilitated transport is accelerated by specific pores, carriers, or permeases, but does not require ATP hydrolysis.

Question 12

Which equation correctly represents the stoichiometry of the Na	extsuperscript{+}-K	extsuperscript{+} ATPase reaction?

Accepted Answer

$$2\mathrm{K}^{+}_{	ext{out}} + 3\mathrm{Na}^{+}_{	ext{in}} + \mathrm{ATP} + \mathrm{H}_2\mathrm{O} ightarrow 2\mathrm{K}^{+}_{	ext{in}} + 3\mathrm{Na}^{+}_{	ext{out}} + \mathrm{ADP} + P_i$$

Question 13

ABC transporters are clinically significant because:

Accepted Answer

They mediate ATP-dependent transport of small molecules and are associated with drug resistance and cystic fibrosis.

Question 14

Which of the following best describes the function of aquaporins in erythrocytes?

Accepted Answer

They facilitate rapid transport of water to maintain osmotic balance and prevent cell rupture.

Question 15

A symport system in a cell membrane:

Accepted Answer

Transports two solutes in the same direction.

Question 16

In the sodium-glucose cotransport system, what provides the energy for glucose transport against its concentration gradient?

Accepted Answer

The sodium gradient across the membrane.

Question 17

Which of the following membrane lipids is most likely to disrupt regular fatty acid chain packing and increase membrane fluidity?

Accepted Answer

Cholesterol

Question 18

Which of the following is a correct statement about the formation of micelles and bilayers?

Accepted Answer

Lipids with one hydrophilic head and two hydrophobic tails form bilayers, while fatty acids tend to form micelles.

Question 19

Which of the following is NOT a major class of membrane-forming lipids?

Accepted Answer

Triacylglycerols

Lipids, Membranes, and Cellular Transport: Structure, Function, and Mechanisms

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