Question 1

Which of the following best explains why membranes rich in unsaturated fatty acids are more fluid than those rich in saturated fatty acids?

Accepted Answer

Unsaturated fatty acids have kinks in their hydrocarbon tails, preventing tight packing of phospholipids.

Question 2

A red blood cell is placed in a solution and swells until it bursts. Which of the following best describes the tonicity of the solution relative to the cell cytoplasm?

Accepted Answer

The solution is hypotonic to the cell.

Question 3

Which of the following statements about the sodium-potassium pump is correct?

Accepted Answer

It moves 3 $$\mathrm{Na^+}$$ ions out of the cell and 2 $$\mathrm{K^+}$$ ions into the cell, using ATP.

Question 4

Which of the following best describes the function of aquaporins in the plasma membrane?

Accepted Answer

They facilitate the rapid diffusion of water across the membrane.

Question 5

A plant cell is placed in a hypertonic solution. What is the most likely outcome for the cell?

Accepted Answer

The cell will lose water and undergo plasmolysis.

Question 6

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

Accepted Answer

Synthesis of phospholipids.

Question 7

A patient with a genetic defect lacks a carrier protein that transports cysteine in kidney cells. What is a likely consequence?

Accepted Answer

Cystine accumulates and forms kidney stones due to failed reabsorption.

Question 8

Which of the following best describes the process of receptor-mediated endocytosis?

Accepted Answer

Specific molecules bind to receptors, triggering vesicle formation for selective uptake.

Question 9

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

Accepted Answer

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

Question 10

Which of the following best explains why cholesterol acts as a 'fluidity buffer' in animal cell membranes?

Accepted Answer

At high temperatures, cholesterol restrains phospholipid movement; at low temperatures, it prevents tight packing.

Question 11

A cell is placed in a solution where the solute concentration is lower outside the cell than inside. Which direction will water move, and what is the likely effect on the cell?

Accepted Answer

Water will move into the cell, causing it to swell.

Question 12

Which of the following is an example of active transport?

Accepted Answer

The sodium-potassium pump moving $$\mathrm{Na^+}$$ out and $$\mathrm{K^+} in $$against their concentration gradients.

Question 13

Which of the following best describes the electrochemical gradient?

Accepted Answer

It is the combined effect of the concentration gradient and membrane potential on ion movement.

Question 14

Which of the following is a real-life example of exocytosis?

Accepted Answer

Pancreatic cells releasing insulin into the bloodstream.

Question 15

Which of the following statements about the fluid mosaic model is correct?

Accepted Answer

Membrane proteins are embedded within the phospholipid bilayer and can move laterally.

Question 16

Which of the following best explains why winter wheat increases the percentage of unsaturated phospholipids in its membranes during autumn?

Accepted Answer

To maintain membrane fluidity at lower temperatures.

Question 17

Which of the following is a correct statement about facilitated diffusion?

Accepted Answer

It requires transport proteins but does not require energy.

Question 18

Which of the following best describes the process of phagocytosis?

Accepted Answer

A cell engulfs a large particle by wrapping pseudopodia around it and packaging it within a vacuole.

Question 19

Which of the following is true regarding the sidedness of membranes?

Accepted Answer

The asymmetrical distribution of proteins, lipids, and carbohydrates is determined during membrane synthesis in the ER and Golgi apparatus.

Membrane Structure and Function – Study Notes for General Biology

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