Question 1

Which of the following best explains why phospholipid bilayers, rather than micelles, are the primary structure of cellular membranes in living cells?

Accepted Answer

Bilayers provide a double layer that separates two aqueous environments, which is necessary for cellular function.

Question 2

A researcher is designing a synthetic vesicle for drug delivery. To maximize the permeability of the vesicle membrane to small, nonpolar drugs, which of the following modifications should they make?

Accepted Answer

Increase the proportion of phospholipids with unsaturated hydrocarbon tails.

Question 3

Which of the following statements about membrane permeability is correct?

Accepted Answer

Increasing temperature generally increases membrane permeability.

Question 4

A cell is placed in a solution and begins to shrink. Which of the following best describes the solution and the process occurring?

Accepted Answer

The solution is hypertonic, and water is leaving the cell by osmosis.

Question 5

Which of the following best describes the movement of oxygen ($O_2$) across a cell membrane?

Accepted Answer

Simple diffusion directly through the phospholipid bilayer.

Question 6

A mutation causes a cell to produce only saturated fatty acids in its membrane phospholipids. What is the most likely effect on the cell's membrane at normal body temperature?

Accepted Answer

The membrane will become less fluid and less permeable.

Question 7

Which of the following scenarios best illustrates active transport?

Accepted Answer

Potassium ions ($K^+$) being pumped into a cell while sodium ions ($Na^+$) are pumped out, both against their concentration gradients.

Question 8

Which of the following best explains why cholesterol decreases membrane permeability at moderate temperatures?

Accepted Answer

Cholesterol increases the packing of phospholipids, reducing the movement of molecules through the membrane.

Question 9

A cell is placed in a solution with a lower solute concentration than its cytoplasm. What will happen to the cell, and what is the term for this type of solution?

Accepted Answer

The cell will swell; the solution is hypotonic.

Question 10

Which of the following is a key feature of the fluid mosaic model of membrane structure?

Accepted Answer

Phospholipids and proteins can move laterally within the layer, creating a dynamic structure.

Question 11

Which of the following best describes facilitated diffusion?

Accepted Answer

Movement of molecules down their concentration gradient through a membrane protein, without energy input.

Question 12

A scientist observes that a certain ion can only cross a cell membrane when a specific protein is present, and the process does not require ATP. Which transport mechanism is most likely involved?

Accepted Answer

Facilitated diffusion

Question 13

Which of the following changes would most likely increase the fluidity and permeability of a cell membrane at room temperature?

Accepted Answer

Increasing the proportion of unsaturated fatty acids in the membrane.

Question 14

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

Accepted Answer

They facilitate the movement of specific molecules and ions across the membrane.

Question 15

A red blood cell is placed in pure water. What will happen to the cell, and why?

Accepted Answer

It will swell and possibly burst because water will enter the cell by osmosis.

Question 16

Which of the following is true regarding the sodium-potassium pump ($Na^+/K^+$-ATPase)?

Accepted Answer

It uses ATP to move sodium ions out of the cell and potassium ions into the cell, both against their gradients.

Question 17

Which of the following best explains why small, nonpolar molecules can cross the phospholipid bilayer easily?

Accepted Answer

They dissolve in the hydrophobic core and move down their concentration gradient.

Question 18

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

Accepted Answer

The cell will lose water and the plasma membrane will pull away from the cell wall (plasmolysis).

Question 19

Which of the following best describes the relationship between membrane fluidity and permeability?

Accepted Answer

As fluidity increases, permeability increases.

Question 20

A cell needs to import glucose against its concentration gradient. Which of the following must be true about the transport process?

Accepted Answer

It requires a transmembrane protein and an input of energy, such as ATP.

Membrane Structure and Transport – Study Notes for General Biology I

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