Question 1

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

Accepted Answer

Their hydrophilic heads interact with water, while their hydrophobic tails avoid water.

Question 2

A patient is given an intravenous solution that is hypertonic relative to their red blood cells. What is the most likely outcome for the cells?

Accepted Answer

The cells will shrink as water leaves the cell to dilute the external solution.

Question 3

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

Accepted Answer

Oxygen ($$\mathrm{O_2$})$$

Question 4

What is the primary function of the sodium-potassium pump ($$\mathrm{Na^+/K^+}-$$ATPase) in animal cells?

Accepted Answer

To move sodium and potassium ions against their concentration gradients using ATP

Question 5

Which of the following statements about facilitated diffusion is correct?

Accepted Answer

It involves membrane proteins that assist the passive movement of molecules down their gradient.

Question 6

A mutation causes a channel protein to lose its selectivity. What is a likely consequence for the cell?

Accepted Answer

The cell may lose control over ion concentrations, disrupting membrane potential.

Question 7

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

Accepted Answer

They have both a hydrophilic head and a hydrophobic tail.

Question 8

Why are unsaturated fats typically liquid at room temperature, while saturated fats are solid?

Accepted Answer

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

Question 9

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

Accepted Answer

Storing genetic information

Question 10

A researcher adds a molecule to a solution containing artificial vesicles. The molecule crosses the membrane only when a specific protein is present, and no ATP is used. What type of transport is this?

Accepted Answer

Facilitated diffusion

Question 11

Which of the following best describes the fluid-mosaic model of membrane structure?

Accepted Answer

Membranes are dynamic, with proteins and lipids able to move laterally within the layer.

Question 12

Which of the following is a key difference between channel proteins and carrier proteins?

Accepted Answer

Channel proteins form open pores for specific ions, while carrier proteins change shape to transport molecules.

Question 13

What is the main role of cholesterol in animal cell membranes?

Accepted Answer

It increases membrane fluidity at low temperatures and decreases it at high temperatures.

Question 14

Which of the following best describes osmosis?

Accepted Answer

The movement of water molecules from low to high solute concentration across a selectively permeable membrane.

Question 15

A cell is placed in a hypotonic solution. What will happen to the cell?

Accepted Answer

It will swell as water enters the cell.

Question 16

Which of the following is true about secondary active transport (cotransport)?

Accepted Answer

It uses the energy stored in an electrochemical gradient to move another molecule against its gradient.

Question 17

Which of the following is a characteristic of steroids?

Accepted Answer

They have a four-ring structure and function as hormones or membrane components.

Question 18

Which of the following best explains why fats store more energy than carbohydrates?

Accepted Answer

Fats have a higher proportion of nonpolar C-H bonds, which store more chemical energy.

Question 19

Which of the following is NOT a property of amphipathic molecules?

Accepted Answer

They dissolve completely in water.

Question 20

Which of the following best describes the role of proteins in the plasma membrane?

Accepted Answer

They allow selective passage of ions and molecules, and can act as receptors or enzymes.

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

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