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 the formula $C_{18}H_{34}O_2$ contains one double bond. Which property would you expect this fatty acid to have compared to stearic acid ($C_{18}H_{36}O_2$)?

Accepted Answer

It would be more fluid and have a lower melting point due to the cis double bond.

Question 3

Which structural feature distinguishes a triacylglycerol from a glycerophospholipid?

Accepted Answer

Triacylglycerols have three fatty acids esterified to glycerol, while glycerophospholipids have two fatty acids and a phosphate-containing head group.

Question 4

Which class of membrane lipids is characterized by a carbohydrate linked to its head group?

Accepted Answer

Glycoglycerolipids

Question 5

Sphingolipids differ from glycerophospholipids in that sphingolipids:

Accepted Answer

Have a fatty acid linked to sphingosine via an amide bond.

Question 6

Which of the following best describes the role of cholesterol in biological membranes?

Accepted Answer

Cholesterol increases membrane fluidity by disrupting fatty acid chain packing.

Question 7

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

Accepted Answer

Cholesterol

Question 8

In the fluid mosaic model of membrane structure, which statement is most accurate?

Accepted Answer

Lipids and proteins diffuse freely within the plane of the membrane, creating a dynamic two-dimensional liquid.

Question 9

Membrane rafts are specialized domains in the membrane that are rich in which components?

Accepted Answer

Cholesterol, sphingolipids, and glycosylphosphatidylinositol

Question 10

Which of the following statements about membrane transport is correct?

Accepted Answer

Facilitated transport uses specific pores, carriers, or permeases to accelerate diffusion.

Question 11

Which equation correctly represents the stoichiometry of the Na$^+$-K$^+$ ATPase reaction?

Accepted Answer

$2K^+_{(out)} + 3Na^+_{(in)} + ATP + H_2O \rightarrow 2K^+_{(in)} + 3Na^+_{(out)} + ADP + P_i$

Question 12

Which of the following is a function of aquaporins in biological membranes?

Accepted Answer

Facilitate rapid transport of water to maintain osmotic balance and preserve ion gradients.

Question 13

A patient with a genetic defect in the Na$^+$-K$^+$ ATPase would most likely experience which physiological consequence?

Accepted Answer

Impaired active transport of sodium and potassium, leading to disrupted cellular ion gradients.

Question 14

Which of the following best describes the difference between symport and antiport cotransport systems?

Accepted Answer

Symport moves two solutes in the same direction; antiport moves two solutes in opposite directions.

Question 15

Which of the following membrane lipids is most likely to form a bilayer rather than a micelle?

Accepted Answer

A lipid with one hydrophilic head group and two hydrophobic tails.

Question 16

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

Accepted Answer

Triacylglycerols

Question 17

Which property of unsaturated fatty acids contributes to increased membrane fluidity?

Accepted Answer

Presence of cis double bonds that introduce kinks and prevent tight packing.

Question 18

Which of the following statements about the amphipathic nature of lipids is correct?

Accepted Answer

Amphipathic lipids have both hydrophobic and hydrophilic regions, allowing them to form bilayers in aqueous environments.

Lipids, Membranes, and Cellular Transport: Structure and Function

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