Question 1

According to the fluid mosaic model, which of the following best describes the structure of the plasma membrane?

Accepted Answer

A double layer of phospholipids with proteins and cholesterol moving laterally within the layer

Question 2

Which of the following molecules would most easily diffuse across a pure phospholipid bilayer without the help of a transport protein?

Accepted Answer

Oxygen (O$$_2)$$

Question 3

A researcher observes that a cell membrane becomes more rigid at low temperatures. Which change in membrane composition would most likely increase membrane fluidity under these conditions?

Accepted Answer

Increasing the proportion of unsaturated fatty acids

Question 4

Which of the following best explains why cholesterol is important for membrane fluidity?

Accepted Answer

It buffers membrane fluidity by preventing tight packing at low temperatures and restraining movement at high temperatures.

Question 5

A red blood cell is placed in a solution and begins to swell and eventually bursts. Which of the following best describes the tonicity of the solution relative to the cell?

Accepted Answer

Hypotonic

Question 6

Which of the following statements about passive transport is correct?

Accepted Answer

It relies on the inherent kinetic energy of molecules and moves substances down their concentration gradients.

Question 7

A cell uses a sodium-potassium pump to move Na$$^+$$ out and K$$^+ in. $$Which of the following best describes the energy requirements and direction of movement for this process?

Accepted Answer

It requires ATP and moves both ions against their concentration gradients.

Question 8

Which of the following best describes the role of membrane potential in cellular function?

Accepted Answer

It is a form of potential energy resulting from the unequal distribution of ions across the membrane.

Question 9

Which of the following scenarios is an example of facilitated diffusion?

Accepted Answer

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

Question 10

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

Accepted Answer

The cell will lose water and undergo plasmolysis.

Question 11

Which of the following best distinguishes integral membrane proteins from peripheral membrane proteins?

Accepted Answer

Integral proteins are embedded within the lipid bilayer, while peripheral proteins are attached to the membrane surface.

Question 12

Which of the following molecules would have the lowest permeability through a pure phospholipid bilayer?

Accepted Answer

Cl$$^-$$

Question 13

Which of the following is a function of membrane proteins?

Accepted Answer

Transporting substances across the membrane

Question 14

A cell is placed in a solution containing a higher concentration of non-permeable solute than inside the cell. What will happen to the cell?

Accepted Answer

Water will move out of the cell, causing it to shrink.

Question 15

Which of the following best describes cotransport across a membrane?

Accepted Answer

The movement of one substance down its gradient drives the active transport of another substance against its gradient

Question 16

Which of the following is an example of active transport?

Accepted Answer

Sodium ions being pumped out of a neuron using ATP

Question 17

Which of the following best explains why large molecules such as proteins and polysaccharides require vesicular transport to cross the plasma membrane?

Accepted Answer

They are too large and hydrophilic to pass through the lipid bilayer or protein channels.

Question 18

Which of the following best describes exocytosis?

Accepted Answer

The fusion of vesicles with the plasma membrane to release contents outside the cell

Question 19

A neuron rapidly transmits signals by opening and closing ion channels. What type of membrane transport is primarily involved in this process?

Accepted Answer

Facilitated diffusion

Question 20

Which of the following best explains why the plasma membrane is described as selectively permeable?

Accepted Answer

It allows some substances to cross more easily than others based on size, polarity, and charge.

Membrane Structure and Function: Study Guide

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