Question 1

Which of the following best describes why phospholipids spontaneously form bilayers in water?

Accepted Answer

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

Question 2

A researcher observes that a certain membrane is highly permeable to oxygen but not to glucose. Which property of the membrane most likely explains this observation?

Accepted Answer

The membrane is selectively permeable, allowing small nonpolar molecules to pass but restricting large polar molecules.

Question 3

Which of the following statements about osmosis is correct?

Accepted Answer

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

Question 4

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

Accepted Answer

It will swell and may burst due to water entering the cell.

Question 5

Which of the following best explains why cholesterol decreases membrane permeability?

Accepted Answer

Cholesterol fills spaces between phospholipid tails, increasing packing density and reducing permeability.

Question 6

Which equation best represents the process of diffusion across a membrane?

Accepted Answer

$$ \Delta G = RT \ln \left( \frac{[C]_2}{[C]_1} \right) $$

Question 7

Which of the following is a function of membrane proteins that cannot be performed by phospholipids alone?

Accepted Answer

Facilitating the diffusion of ions and large polar molecules across the membrane.

Question 8

A mutation causes the CFTR protein to become nonfunctional. Which physiological effect would most likely result?

Accepted Answer

Chloride ions would accumulate inside cells, leading to thick mucus in the lungs.

Question 9

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

Accepted Answer

Facilitated diffusion uses channel or carrier proteins to move substances down their gradient without energy input, while active transport requires energy to move substances against their gradient.

Question 10

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.

Question 11

A scientist creates an artificial membrane with only short, unsaturated hydrocarbon tails. Which property will this membrane most likely exhibit?

Accepted Answer

High permeability to small, nonpolar molecules.

Question 12

Which of the following is true about the sodium-potassium pump ($$ 	ext{Na}^+/	ext{K}^+ -$$ATPase)?

Accepted Answer

It requires ATP to function.

Question 13

Which of the following best describes secondary active transport (co-transport)?

Accepted Answer

It uses the energy stored in an electrochemical gradient to move another molecule against its gradient.

Question 14

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

Accepted Answer

Acting as enzymes to catalyze reactions.

Question 15

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

Accepted Answer

The membrane is a dynamic mosaic of phospholipids and proteins that can move laterally within the layer.

Question 16

Which of the following best explains why plant cells do not burst in a hypotonic solution?

Accepted Answer

Plant cells have a rigid cell wall that prevents excessive swelling.

Question 17

Which of the following is a property of amphipathic molecules?

Accepted Answer

They contain both hydrophilic and hydrophobic regions.

Question 18

Which of the following experimental techniques was crucial in supporting the fluid-mosaic model of membranes?

Accepted Answer

Freeze-fracture electron microscopy showing proteins embedded within the bilayer.

Question 19

Which of the following best describes the role of aquaporins in the cell membrane?

Accepted Answer

They allow water to cross the membrane rapidly via facilitated diffusion.

Question 20

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

Accepted Answer

There will be no net movement of water, and the cell size will remain the same.

CH. 6 - Lipids, Membranes, and the First Cells: Structure, Function, and Transport

Guida di studio - Domande di pratica

Study guide - Flashcard