Question 1

Which of the following best explains why lipids are hydrophobic?

Accepted Answer

They are composed primarily of hydrocarbons, which share electrons equally in C–H bonds.

Question 2

Which structural feature distinguishes a saturated fatty acid from an unsaturated fatty acid?

Accepted Answer

Saturated fatty acids have no double bonds, while unsaturated fatty acids have at least one double bond, causing a kink in the chain.

Question 3

Which of the following is a function of cholesterol in animal cell membranes?

Accepted Answer

It decreases membrane permeability by filling spaces between phospholipids.

Question 4

A triacylglycerol (fat) molecule is formed by which type of reaction?

Accepted Answer

Dehydration reaction between three fatty acids and one glycerol, forming ester linkages.

Question 5

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

Accepted Answer

A glycerol backbone attached to two fatty acids and a phosphate group.

Question 6

Why do unsaturated fatty acids increase membrane fluidity?

Accepted Answer

Their double bonds create kinks, preventing close packing of hydrocarbon tails.

Question 7

Which of the following statements about membrane permeability is correct?

Accepted Answer

Membranes with short, unsaturated hydrocarbon tails are more permeable than those with long, saturated tails.

Question 8

Which of the following molecules would most easily cross a pure phospholipid bilayer?

Accepted Answer

O$$_2$$

Question 9

What is the main reason that saturated fats are solid at room temperature while unsaturated fats are liquid?

Accepted Answer

Unsaturated fats have double bonds that create kinks, preventing tight packing.

Question 10

Which of the following best describes the amphipathic nature of phospholipids?

Accepted Answer

They have both hydrophilic and hydrophobic regions.

Question 11

A researcher increases the cholesterol content in an artificial membrane. What is the most likely effect on the membrane’s permeability to glycerol?

Accepted Answer

Permeability to glycerol will decrease.

Question 12

Which of the following is NOT a function of membrane proteins?

Accepted Answer

Synthesizing phospholipids from fatty acids.

Question 13

Which of the following best explains why cystic fibrosis affects the lungs?

Accepted Answer

A defective CFTR protein reduces chloride ion flow, leading to thick mucus that traps bacteria.

Question 14

Which of the following statements about steroid hormones is correct?

Accepted Answer

They are composed of four fused hydrocarbon rings.

Question 15

Which of the following changes would most likely increase the fluidity of a cell membrane at low temperature?

Accepted Answer

Increasing the proportion of unsaturated fatty acids.

Question 16

A mutation causes a cell to produce phospholipids with much longer hydrocarbon tails. What is the most likely effect on the cell membrane?

Accepted Answer

The membrane will become less fluid and less permeable.

Question 17

Which of the following best describes the effect of temperature on membrane permeability?

Accepted Answer

Permeability increases as temperature increases.

Question 18

Which of the following is a correct statement about the structure-function relationship in the CFTR protein?

Accepted Answer

The structure of CFTR allows it to function as a chloride channel, and mutations that alter its structure disrupt this function.

Question 19

Which of the following best explains why polyunsaturated lipids may help prevent heart disease?

Accepted Answer

They contain multiple double bonds, which increase membrane fluidity and may reduce cholesterol buildup.

Question 20

Which of the following best describes the role of isoprenoids in biological systems?

Accepted Answer

They function as pigments, scents, vitamins, and sex hormone precursors.

Lipids, Membranes, and the First Cells: Structure and Function

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