Question 1

Which of the following best explains why phospholipids form bilayers in aqueous environments?

Accepted Answer

Their hydrophilic heads interact with water, while their hydrophobic tails avoid it.

Question 2

A cell is placed in a solution with a lower solute concentration than its cytoplasm. What will most likely happen to the cell?

Accepted Answer

Water will enter the cell, causing it to swell and possibly lyse.

Question 3

Which equation correctly represents the calculation of diffusion rate ($$J) $$across a membrane according to Fick's Law?

Accepted Answer

$$J = D \frac{(C_2$ - C_1$)}{d}$$

Question 4

Which of the following statements about saturated and unsaturated fatty acids is correct?

Accepted Answer

Unsaturated fatty acids have at least one double bond, causing kinks in their structure.

Question 5

A patient is given intravenous fluids that are hypotonic compared to their blood plasma. What is the most likely effect on their red blood cells?

Accepted Answer

Red blood cells will gain water and may burst (lyse).

Question 6

Which of the following best describes the role of cholesterol in animal cell membranes?

Accepted Answer

It stabilizes membrane fluidity by preventing tight packing of phospholipids at low temperatures and restricting movement at high temperatures.

Question 7

Which process requires energy input from the cell to move substances against their concentration gradient?

Accepted Answer

Active transport

Question 8

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

Accepted Answer

Water will leave the cell, causing the cell membrane to pull away from the cell wall (plasmolysis).

Question 9

Which of the following is a function of membrane proteins?

Accepted Answer

They facilitate transport, act as enzymes, and serve as receptors.

Question 10

Which statement best describes the difference between passive and active transport?

Accepted Answer

Active transport moves substances against their concentration gradient using energy, while passive transport moves substances down their gradient without energy input.

Question 11

Which of the following molecules can most easily cross the plasma membrane by simple diffusion?

Accepted Answer

Small nonpolar molecules like $$O_2$$ and $$CO_2$$

Question 12

A cell uses the sodium-potassium pump to maintain ion gradients. Which equation best represents the stoichiometry of ions moved per ATP hydrolyzed?

Accepted Answer

$$3 \ Na^+$$ out, $$2 \ K^+ in$

Question 13

Which of the following best describes facilitated diffusion?

Accepted Answer

Movement of molecules through the membrane via carrier or channel proteins, down their concentration gradient, without energy input.

Question 14

Which of the following is NOT a function of lipids in biological systems?

Accepted Answer

Catalyzing chemical reactions

Question 15

Which of the following statements about osmosis is correct?

Accepted Answer

Osmosis is the movement of water across a selectively permeable membrane from low solute concentration to high solute concentration.

Question 16

Which of the following best explains why unsaturated fatty acids increase membrane fluidity?

Accepted Answer

Their double bonds create kinks, preventing tight packing of phospholipids.

Question 17

A cell is placed in an isotonic solution. What will happen to the cell?

Accepted Answer

There will be no net movement of water into or out of the cell.

Question 18

Which of the following is a correct description of the fluid mosaic model of the plasma membrane?

Accepted Answer

The membrane is a dynamic structure with proteins and lipids able to move laterally within the bilayer.

Question 19

Which of the following best describes the movement of glucose into a cell via a glucose transporter protein?

Accepted Answer

Facilitated diffusion down its concentration gradient

Lipids, Membranes, and Membrane Transport in Cells

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