Question 1

Which of the following best explains why phospholipids spontaneously form bilayers in aqueous environments?

Accepted Answer

Phospholipids are amphipathic, with hydrophilic heads and hydrophobic tails, causing them to arrange into bilayers to minimize free energy.

Question 2

Which of the following is NOT a function of fats (triglycerides) in biological systems?

Accepted Answer

Serving as a major component of cell membranes.

Question 3

Steroids are distinguished from other lipids by which structural feature?

Accepted Answer

A bulky, four-ring structure.

Question 4

Which of the following statements about membrane fluidity is correct?

Accepted Answer

Membrane fluidity is increased by a high proportion of unsaturated fatty acids due to kinks in their tails.

Question 5

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

Accepted Answer

They have both a hydrophilic (polar) head and hydrophobic (nonpolar) tails.

Question 6

Cholesterol is considered amphipathic because:

Accepted Answer

It contains both a polar hydroxyl group and a nonpolar hydrocarbon region.

Question 7

Which of the following is a direct consequence of the amphipathic nature of phospholipids in water?

Accepted Answer

Spontaneous formation of lipid bilayers.

Question 8

A cell membrane is described as 'more than just a lipid bilayer' because:

Accepted Answer

It contains proteins and other molecules that contribute to its function.

Question 9

Which of the following best explains why unsaturated fatty acids increase membrane fluidity?

Accepted Answer

The kinks caused by double bonds prevent tight packing of phospholipids.

Question 10

Which of the following is NOT a property of cell membranes?

Accepted Answer

They are completely rigid and inflexible.

Question 11

A researcher adds a large amount of cholesterol to a cell membrane at room temperature. What is the most likely effect on membrane fluidity?

Accepted Answer

Membrane fluidity will decrease because cholesterol fills spaces between phospholipids.

Question 12

Which of the following equations best represents the dehydration reaction that forms a triglyceride?

Accepted Answer

$$ 	ext{Glycerol} + 3 	imes 	ext{Fatty Acid} ightarrow 	ext{Triglyceride} + 3 	imes 	ext{H}_2	ext{O} $$

Question 13

Which of the following best describes the role of the cell membrane as a selective barrier?

Accepted Answer

It allows some substances to cross more easily than others, maintaining the internal environment.

Question 14

Which of the following is a key difference between fats and phospholipids?

Accepted Answer

Fats have three fatty acid tails, while phospholipids have two fatty acid tails and a phosphate group.

Question 15

A mutation causes a cell to produce phospholipids with only saturated fatty acids. What is the most likely effect on the cell membrane at room temperature?

Accepted Answer

The membrane will become less fluid and more rigid.

Question 16

Which of the following is true about the permeability of the phospholipid bilayer?

Accepted Answer

Small, nonpolar molecules can cross easily, while large or charged molecules require transport proteins.

Question 17

Which of the following best explains why closed phospholipid bilayers (vesicles) are more stable than open sheets in aqueous solution?

Accepted Answer

Closed bilayers eliminate exposure of hydrophobic tails to water.

Question 18

Which of the following is NOT a characteristic of steroids?

Accepted Answer

They are formed by linking fatty acids into long chains.

Question 19

Which of the following best describes the relationship between membrane fluidity and cell function?

Accepted Answer

Increased fluidity allows for cell shape changes, division, and membrane fusion.

Lipids, Membranes, and Transport: Structure and Function in Cells

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