Question 1

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

Accepted Answer

A double layer of phospholipids with proteins and carbohydrates embedded and moving within the layer.

Question 2

Which component of the plasma membrane is primarily responsible for its selective permeability to ions and polar molecules?

Accepted Answer

Integral membrane proteins

Question 3

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

Accepted Answer

The cell will swell and may burst because water moves in due to osmosis.

Question 4

Which of the following statements about membrane fluidity is correct?

Accepted Answer

Membrane fluidity increases with a higher proportion of unsaturated fatty acids.

Question 5

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

Question 6

Which of the following molecules is LEAST likely to diffuse directly through the phospholipid bilayer of a cell membrane?

Accepted Answer

Na$$^+ ($$sodium ion)

Question 7

A cell is placed in a solution with a higher solute concentration than its cytoplasm. Which term best describes the solution, and what will happen to the cell?

Accepted Answer

Hypertonic; the cell will shrink.

Question 8

Which of the following best explains why large polar molecules require transport proteins to cross the plasma membrane?

Accepted Answer

They are too large to fit between the phospholipids and are repelled by the hydrophobic core.

Question 9

Which process is responsible for the uptake of specific macromolecules into a cell via binding to membrane proteins and formation of coated vesicles?

Accepted Answer

Receptor-mediated endocytosis

Question 10

A scientist observes that a cell is able to import glucose even when the concentration of glucose is higher inside the cell than outside. Which transport mechanism is most likely responsible?

Accepted Answer

Active transport via a carrier protein

Question 11

Which of the following equations best represents the relationship between solute concentration and osmotic pressure ($$\Pi) at a $$constant temperature, according to van 't Hoff's law?

Accepted Answer

$$\Pi = CRT$$

Question 12

Which of the following is an example of secondary active transport (cotransport) in cells?

Accepted Answer

Uptake of glucose into intestinal cells using the Na$$^+$$ gradient

Question 13

Which statement best explains why cholesterol is important for membrane fluidity in animal cells?

Accepted Answer

Cholesterol prevents the membrane from becoming too rigid at low temperatures and too fluid at high temperatures.

Question 14

Which of the following best describes the function of glycoproteins and glycolipids in the plasma membrane?

Accepted Answer

They are involved in cell-cell recognition and signaling.

Question 15

A neuron maintains a membrane potential of approximately $$-70 mV. $$Which of the following best explains the role of the sodium-potassium pump in this process?

Accepted Answer

It pumps Na$$^+$$ out of the cell and K$$^+$$ into the cell, creating an electrochemical gradient.

Question 16

Which of the following scenarios best illustrates the concept of facilitated diffusion?

Accepted Answer

Glucose entering a muscle cell through a specific carrier protein down its concentration gradient.

Question 17

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

Accepted Answer

Storing genetic information

Question 18

During exocytosis, which of the following events occurs?

Accepted Answer

A vesicle fuses with the plasma membrane, releasing its contents outside the cell.

Question 19

Which of the following best describes the difference between simple diffusion and facilitated diffusion?

Accepted Answer

Facilitated diffusion requires transport proteins, while simple diffusion does not.

Question 20

A plant cell is placed in a hypertonic solution. What is the most likely effect on the cell, and what is this process called?

Accepted Answer

The cell will lose water and the plasma membrane will pull away from the cell wall; this is called plasmolysis.

Membrane Structure and Function: Study Notes

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