Question 1

Which of the following best describes the structure of a phospholipid in the plasma membrane?

Accepted Answer

A molecule with a hydrophilic head and two hydrophobic tails

Question 2

The fluid mosaic model of the plasma membrane suggests that:

Accepted Answer

Proteins are embedded within a fluid phospholipid bilayer and can move laterally

Question 3

Which of the following substances is most likely to diffuse directly through the phospholipid bilayer of a plasma membrane?

Accepted Answer

Oxygen ($$O_2)$$

Question 4

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

Accepted Answer

It will gain water and burst (lyse)

Question 5

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

Accepted Answer

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

Question 6

Which type of membrane transport requires energy input from the cell?

Accepted Answer

Active transport

Question 7

A plant cell placed in a hypertonic solution will:

Accepted Answer

Become plasmolyzed as water leaves the cell

Question 8

Which of the following statements about membrane proteins is correct?

Accepted Answer

Transmembrane proteins can function as channels, receptors, or enzymes

Question 9

Facilitated diffusion differs from simple diffusion in that facilitated diffusion:

Accepted Answer

Requires transport proteins to move substances down their concentration gradient

Question 10

Which of the following best describes the function of a proton pump in the plasma membrane?

Accepted Answer

It uses ATP to move protons ($$H^+) $$against their concentration gradient, creating an electrochemical gradient

Question 11

A cell uses a sodium-potassium pump to move $$Na^+$$ ions out and $$K^+$$ ions in. Which type of transport is this and what is the energy source?

Accepted Answer

Active transport; energy from ATP hydrolysis ($$ATP \rightarrow ADP + P_i)$$

Question 12

Which of the following is an example of bulk transport across the plasma membrane?

Accepted Answer

Endocytosis

Question 13

A cell is placed in an isotonic solution. What will happen to the net movement of water?

Accepted Answer

There will be no net movement of water

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 function of membrane carbohydrates?

Accepted Answer

Attachment to the cytoskeleton

Question 16

A scientist observes that a certain molecule cannot cross the plasma membrane without the help of a protein, but the process does not require energy. What type of transport is this?

Accepted Answer

Facilitated diffusion

Question 17

Which of the following scenarios best illustrates cotransport?

Accepted Answer

A proton pump uses ATP to move $$H^+$$ out of the cell, and the return of $$H^+$$ down its gradient drives the uptake of sucrose

Question 18

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

Accepted Answer

They facilitate the movement of specific molecules across the membrane

Question 19

If a cell's membrane becomes too rigid due to low temperature, which adaptation would help restore fluidity?

Accepted Answer

Increasing the proportion of unsaturated fatty acids

Question 20

Which of the following is a real-life example of selective permeability in the plasma membrane?

Accepted Answer

Oxygen ($$O_2) $$diffuses into lung cells while sodium ions ($$Na^+) $$require transport proteins to enter

Membrane Structure and Function: Study Notes for General Biology

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