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 embedded and moving within the layer.

Question 2

Which property of phospholipids is most responsible for the formation of the bilayer structure in cell membranes?

Accepted Answer

Their amphipathic nature, having both hydrophobic and hydrophilic regions.

Question 3

A researcher cools a sample of animal cell membranes and observes that the membranes become less fluid and more solid. Which change in membrane composition would most likely counteract this effect?

Accepted Answer

Increasing the proportion of unsaturated fatty acids in the phospholipids.

Question 4

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

Accepted Answer

Oxygen ($O_2$)

Question 5

A cell is placed in a solution and water moves into the cell, causing it to swell and potentially burst. Which term best describes the tonicity of the solution relative to the cell?

Accepted Answer

Hypotonic

Question 6

Which of the following statements about facilitated diffusion is correct?

Accepted Answer

It involves transport proteins that move substances down their concentration gradient.

Question 7

The sodium-potassium pump is an example of which type of membrane transport?

Accepted Answer

Active transport

Question 8

Which of the following best explains why ions such as $Na^+$ and $K^+$ require transport proteins to cross the plasma membrane?

Accepted Answer

They are hydrophilic and cannot pass through the hydrophobic core of the membrane.

Question 9

A patient with severe diarrhea is given a solution containing both sodium chloride and glucose. Why is this treatment effective in rehydrating the patient?

Accepted Answer

Glucose and sodium ions are co-transported into intestinal cells, increasing water absorption by osmosis.

Question 10

Which of the following best describes the function of an electrogenic pump?

Accepted Answer

It generates voltage across the membrane by moving ions.

Question 11

Which process involves the uptake of specific molecules into the cell via vesicles formed after binding to cell-surface receptors?

Accepted Answer

Receptor-mediated endocytosis

Question 12

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

Accepted Answer

It will lose water and shrink.

Question 13

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

Accepted Answer

Energy storage

Question 14

Which of the following best explains why the inside of a typical animal cell is negative relative to the outside?

Accepted Answer

The sodium-potassium pump moves more positive ions out than in, creating a net negative charge inside.

Question 15

Which of the following scenarios best illustrates cotransport (secondary active transport)?

Accepted Answer

The downhill movement of $Na^+$ into the cell drives the uphill transport of glucose into the cell.

Question 16

Which of the following statements about exocytosis is correct?

Accepted Answer

It involves the fusion of vesicles with the plasma membrane to release contents outside the cell.

Question 17

A mutation causes a cell to lack functional CCR5 co-receptors on its surface. What is a likely consequence of this mutation?

Accepted Answer

The cell will be resistant to HIV infection.

Question 18

Which of the following best describes the movement of water across a selectively permeable membrane?

Accepted Answer

Water moves from a region of lower solute concentration to higher solute concentration.

Question 19

Which of the following is true about the lateral movement of phospholipids and proteins in the plasma membrane?

Accepted Answer

Most phospholipids and some proteins can move laterally within the membrane.

Question 20

A nerve cell responds to an electrical stimulus by opening potassium ion channels. What type of membrane protein is involved in this process?

Accepted Answer

A channel protein that opens in response to a stimulus

Membrane Structure and Function – Chapter 7 Study Notes

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