Question 1

Which of the following best describes the structure of a biological membrane according to the fluid mosaic model?

Accepted Answer

A continuous bilayer of phospholipids in which proteins float like icebergs in a sea.

Question 2

Which component of the cell membrane is primarily responsible for modulating membrane fluidity in animal cells?

Accepted Answer

Cholesterol

Question 3

A researcher observes that a membrane protein can move laterally within the phospholipid bilayer but cannot move to another region of the membrane. What is the most likely explanation for this restriction?

Accepted Answer

The protein is attached to the cytoskeleton inside the cell.

Question 4

Which of the following molecules is LEAST likely to cross the phospholipid bilayer by simple diffusion?

Accepted Answer

Glucose

Question 5

Which equation correctly represents osmotic pressure ($$\Pi) $$across a membrane?

Accepted Answer

$$\Pi = cRT$$

Question 6

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

Accepted Answer

It will swell and may burst due to water influx.

Question 7

Which of the following statements about passive transport is TRUE?

Accepted Answer

It moves substances down their concentration gradient without energy input.

Question 8

Membrane fluidity is increased by which of the following changes?

Accepted Answer

Increasing the proportion of short, unsaturated fatty acid chains.

Question 9

Which type of membrane protein is at least partly embedded in the phospholipid bilayer?

Accepted Answer

Integral membrane protein

Question 10

A cell is placed in a solution with a higher solute concentration than its cytoplasm. What type of solution is this, and what is the expected net movement of water?

Accepted Answer

Hypertonic; water moves out of the cell

Question 11

Which of the following best explains why polar molecules such as glucose require facilitated diffusion to cross the cell membrane?

Accepted Answer

They are repelled by the hydrophobic interior of the phospholipid bilayer.

Question 12

Which of the following is a function of carbohydrates on the outer surface of the cell membrane?

Accepted Answer

Facilitating cell-cell recognition and communication

Question 13

Which factor does NOT directly affect the rate of diffusion of a solute across a membrane?

Accepted Answer

Presence of cholesterol in the membrane

Question 14

Which of the following best describes the movement of water during osmosis?

Accepted Answer

Water moves from a region of low solute concentration to high solute concentration.

Question 15

A scientist measures the rate of diffusion of a small molecule at two different temperatures. At which temperature will the molecule diffuse faster, and why?

Accepted Answer

At the higher temperature, because molecules have more kinetic energy.

Question 16

Which of the following is TRUE about transmembrane proteins?

Accepted Answer

They extend through the bilayer and may have domains on both sides.

Question 17

Which process requires metabolic energy to move substances across the membrane?

Accepted Answer

Active transport

Question 18

Which of the following is a real-life example of selective permeability in biological membranes?

Accepted Answer

Oxygen entering lung cells while sodium ions are blocked without a channel.

Question 19

A cell is placed in an isotonic solution. What will happen to the cell?

Accepted Answer

It will remain unchanged.

Question 20

Which of the following best explains why cholesterol is important in animal cell membranes?

Accepted Answer

It interacts with polar heads of phospholipids to modulate membrane fluidity.

Cell Membranes & Transport: Structure, Function, and Mechanisms

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