Q: Which equation correctly represents the net movement of water during osmosis across a selectively permeable membrane?

$\Delta \text{Water} = \text{Water}_{hypotonic} - \text{Water}_{hypertonic}$

Question 1

Which statement best describes the fluid mosaic model of the plasma membrane?

Accepted Answer

The membrane is a fluid structure with proteins embedded or attached to a double layer of phospholipids.

Question 2

What property of phospholipids is essential for the formation of biological membranes?

Accepted Answer

They are amphipathic molecules, possessing both hydrophobic and hydrophilic regions.

Question 3

Which of the following would most likely increase the fluidity of a cell membrane at low temperatures?

Accepted Answer

Increasing the proportion of unsaturated fatty acids in phospholipids.

Question 4

A red blood cell placed in a hypotonic solution will:

Accepted Answer

Gain water, swell, and potentially burst (lyse).

Question 5

Which equation correctly represents the net movement of water during osmosis across a selectively permeable membrane?

Accepted Answer

$\Delta 	ext{Water} = 	ext{Water}_{hypotonic} - 	ext{Water}_{hypertonic}$

Question 6

Which type of membrane protein is most likely to be involved in cell-cell recognition?

Accepted Answer

Glycoproteins with branched oligosaccharides on the external surface.

Question 7

The Na$^+$-K$^+$ pump moves ions against their concentration gradients. Which of the following best describes the energy source and stoichiometry of this pump?

Accepted Answer

It uses ATP to pump three Na$^+$ ions out and two K$^+$ ions in.

Question 8

Which of the following molecules would most easily diffuse through the lipid bilayer of a plasma membrane?

Accepted Answer

O$_2$

Question 9

A plant cell in a hypertonic solution will most likely:

Accepted Answer

Lose water, causing the plasma membrane to pull away from the cell wall (plasmolysis).

Question 10

Which process is responsible for the bulk uptake of specific molecules, such as cholesterol, into animal cells?

Accepted Answer

Receptor-mediated endocytosis

Question 11

Which of the following best explains why membrane proteins are amphipathic?

Accepted Answer

They have regions that interact with both the hydrophobic core and the aqueous environment.

Question 12

Which of the following is a real-world consequence of defective LDL receptors in human cells?

Accepted Answer

Accumulation of cholesterol in the blood, leading to early atherosclerosis.

Question 13

Which of the following equations best represents the energy change associated with diffusion down a concentration gradient?

Accepted Answer

$\Delta G < 0$

Question 14

Which type of transport protein undergoes a conformational change to move its substrate across the membrane?

Accepted Answer

Carrier protein

Question 15

Which of the following statements about facilitated diffusion is correct?

Accepted Answer

It moves molecules down their concentration gradient via transport proteins.

Question 16

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

Accepted Answer

It restrains the movement of phospholipids, reducing membrane fluidity.

Question 17

Which of the following is an example of cotransport (secondary active transport) in cells?

Accepted Answer

A proton pump creating a gradient used to drive the uptake of sucrose via a symport protein.

Question 18

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 charged and hydrophilic, so they cannot pass through the hydrophobic core of the membrane.

Question 19

Which process is most directly responsible for the secretion of insulin from pancreatic cells?

Accepted Answer

Exocytosis

Question 20

Which of the following best describes the movement of Na$^+$ ions into a nerve cell when a gated channel opens?

Accepted Answer

Na$^+$ ions move down their electrochemical gradient, which includes both concentration and electrical forces.

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