Q: Which of the following equations correctly represents the direction of water movement during osmosis?

$\text{Water moves from low } [\text{solute}] \rightarrow \text{high } [\text{solute}]$ across a selectively permeable membrane.

Question 1

Which of the following best explains why phospholipid bilayers form spontaneously in water?

Accepted Answer

The hydrophobic tails of phospholipids avoid water, while the hydrophilic heads interact with water, leading to bilayer formation.

Question 2

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

Accepted Answer

The solution is hypertonic relative to the cell, causing water to move out by osmosis.

Question 3

Which of the following molecules would most easily cross a pure phospholipid bilayer?

Accepted Answer

Carbon dioxide ($\mathrm{CO_2}$)

Question 4

Which factor would increase the permeability of a phospholipid bilayer to water?

Accepted Answer

Increasing the number of unsaturated fatty acids in the membrane.

Question 5

A cell uses a protein to move glucose from a region of high concentration to a region of low concentration. Which type of transport is this?

Accepted Answer

Facilitated diffusion

Question 6

Which of the following statements about the fluid-mosaic model of membranes is correct?

Accepted Answer

Membranes are composed of a mosaic of lipids and proteins that can move laterally within the layer.

Question 7

Which of the following best describes active transport?

Accepted Answer

Movement of molecules against their concentration gradient using energy, often from ATP.

Question 8

A mutation causes a cell to produce phospholipids with much longer fatty acid tails. What is the most likely effect on the cell membrane?

Accepted Answer

The membrane will become less fluid and less permeable.

Question 9

Which of the following is a real-life example of facilitated diffusion?

Accepted Answer

Glucose transport into muscle cells via GLUT transporters.

Question 10

Which of the following equations correctly represents the direction of water movement during osmosis?

Accepted Answer

$	ext{Water moves from low } [	ext{solute}] ightarrow 	ext{high } [	ext{solute}]$ across a selectively permeable membrane.

Question 11

Which of the following changes would most likely DECREASE the rate of simple diffusion of oxygen ($\mathrm{O_2}$) across a cell membrane?

Accepted Answer

Decreasing the temperature of the environment.

Question 12

A patient is given an intravenous (IV) solution that is hypotonic relative to their blood cells. What is the most likely outcome?

Accepted Answer

Water will enter the blood cells, causing them to swell and possibly burst.

Question 13

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

Accepted Answer

Cholesterol decreases membrane permeability by filling spaces between phospholipids.

Question 14

Which of the following statements about membrane proteins is correct?

Accepted Answer

Some membrane proteins span the entire bilayer and function as channels or transporters.

Question 15

The Na+/K+ ATPase pump moves sodium and potassium ions across the plasma membrane. Which of the following is true about this process?

Accepted Answer

It moves sodium out of the cell and potassium into the cell, both against their concentration gradients, using ATP.

Question 16

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

Accepted Answer

Increasing the proportion of unsaturated fatty acids in the phospholipids.

Question 17

A scientist observes that a certain molecule cannot cross a pure phospholipid bilayer but can enter cells rapidly. Which is the most likely explanation?

Accepted Answer

The molecule enters cells via a specific transport protein.

Question 18

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

Accepted Answer

Facilitated diffusion requires a membrane protein, while simple diffusion does not.

Question 19

Which of the following scenarios best illustrates the concept of selective permeability?

Accepted Answer

A cell membrane allows oxygen to pass freely but restricts the movement of glucose.

Question 20

Which of the following is NOT a factor that influences membrane permeability?

Accepted Answer

The number of ribosomes in the cell.

Chapter 6: Lipids, Membranes, and the First Cells – Study Notes

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