Question 1

Which of the following best describes the 'fluid mosaic model' of the plasma membrane?

Accepted Answer

A dynamic structure where phospholipids and proteins can move laterally within the layer, with various proteins and other molecules embedded throughout.

Question 2

Which component of the plasma membrane is primarily responsible for its selective permeability?

Accepted Answer

The phospholipid bilayer, due to its hydrophobic core, and the specific membrane proteins that regulate passage of certain molecules.

Question 3

How does cholesterol affect membrane fluidity at different temperatures?

Accepted Answer

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

Question 4

A red blood cell is placed in a hypotonic solution. What is the most likely outcome?

Accepted Answer

The cell will gain water, swell, and may burst (lyse).

Question 5

Which of the following best describes facilitated diffusion?

Accepted Answer

Passive movement of molecules down their concentration gradient through a specific transmembrane protein.

Question 6

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

Accepted Answer

Synthesizing phospholipids for the membrane.

Question 7

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

Accepted Answer

It will become plasmolyzed as water leaves the cell and the plasma membrane pulls away from the cell wall.

Question 8

Which of the following statements about passive and active transport is correct?

Accepted Answer

Active transport moves substances against their concentration gradient, requiring energy, while passive transport moves substances down their concentration gradient without energy input.

Question 9

Which process is responsible for the uptake of large solid particles, such as bacteria, by a white blood cell?

Accepted Answer

Phagocytosis

Question 10

A solution contains 0.2 M glucose on side A and 0.1 M glucose on side B, separated by a membrane permeable only to water. Which direction will water move?

Accepted Answer

From side B to side A

Question 11

Which of the following best describes an amphipathic molecule?

Accepted Answer

A molecule that has both hydrophilic and hydrophobic regions.

Question 12

Which of the following is an example of active transport?

Accepted Answer

The sodium-potassium pump moving $$\mathrm{Na^+}$$ out of and $$\mathrm{K^+}$$ into a cell using ATP.

Question 13

Which of the following statements about osmosis is correct?

Accepted Answer

Osmosis is the passive movement of water across a selectively permeable membrane from a region of low solute concentration to high solute concentration.

Question 14

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

Accepted Answer

Their kinks prevent tight packing of phospholipids, increasing fluidity.

Question 15

Which of the following is NOT a bulk transport mechanism used by cells?

Accepted Answer

Facilitated diffusion

Question 16

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

Accepted Answer

There will be no net movement of water; the cell will remain stable.

Question 17

Which of the following best describes receptor-mediated endocytosis?

Accepted Answer

The cell takes in specific molecules after they bind to receptors on the cell surface, forming a vesicle.

Question 18

Which of the following best describes the movement of molecules 'down a concentration gradient'?

Accepted Answer

Movement from an area of high concentration to low concentration.

Question 19

Which of the following scenarios best illustrates the concept of selective permeability?

Accepted Answer

A membrane that allows water and small nonpolar molecules to pass, but restricts ions and large polar molecules unless specific proteins are present.

Question 20

Which of the following is a correct statement about the hydrophobic and hydrophilic regions of a phospholipid?

Accepted Answer

The fatty acid tails are hydrophobic and the phosphate head is hydrophilic.

Chapter 7nMembrane Structure and Function-REVIEW

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