Q: Which equation best represents the electrochemical gradient across a membrane?

$$\\Delta G = RT \\ln \\left( \\frac{[C]_i}{[C]_o} \\right) + zF\\Delta \\Psi$$

Question 1

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

Accepted Answer

Their amphipathic nature causes hydrophilic heads to interact with water and hydrophobic tails to avoid water.

Question 2

A cell membrane is exposed to cold temperatures. Which change would most likely help maintain membrane fluidity?

Accepted Answer

Increase the proportion of unsaturated fatty acids in the membrane.

Question 3

Which statement about lipids is correct?

Accepted Answer

Lipids are hydrophobic macromolecules not made up of monomers.

Question 4

What is the primary reason that cholesterol is considered amphipathic?

Accepted Answer

It contains both a polar hydroxyl group and a nonpolar hydrocarbon region.

Question 5

Which of the following would most likely increase the permeability of a phospholipid bilayer?

Accepted Answer

Increasing the proportion of unsaturated fatty acids.

Question 6

A researcher creates two artificial membranes: one with short, unsaturated hydrocarbon tails and one with long, saturated hydrocarbon tails. Which membrane will have higher fluidity and why?

Accepted Answer

The membrane with short, unsaturated tails due to decreased van der Waals interactions.

Question 7

Which equation best represents the electrochemical gradient across a membrane?

Accepted Answer

$$\Delta G = RT \ln \left( \frac{[C]_i}{[C]_o} \right) + zF\Delta \Psi$$

Question 8

Facilitated diffusion through a potassium channel is an example of which type of membrane transport?

Accepted Answer

Facilitated diffusion

Question 9

Which of the following best describes the movement of phospholipids within a bilayer?

Accepted Answer

Phospholipids move laterally within the bilayer but rarely flip to the other side.

Question 10

A cell needs to transport a large, charged molecule across its membrane. Which transport mechanism is most likely to be used?

Accepted Answer

Facilitated diffusion via a carrier protein

Question 11

Which of the following statements about membrane pumps is correct?

Accepted Answer

They require energy input, often from ATP, to move substances against their gradient.

Question 12

Which property of phospholipids is most important for the formation of cell membranes?

Accepted Answer

Their amphipathic nature, with both hydrophilic and hydrophobic regions.

Question 13

Which of the following changes would decrease the fluidity of a cell membrane at normal body temperature?

Accepted Answer

Increasing the proportion of saturated fatty acids.

Question 14

Which of the following is NOT a component of a phospholipid?

Accepted Answer

Amino acid

Question 15

What effect does cholesterol have on membrane fluidity at low temperatures?

Accepted Answer

It increases fluidity by preventing tight packing of phospholipids.

Question 16

Which of the following best describes the structure of a phospholipid?

Accepted Answer

A polar head group, a phosphate group, a glycerol backbone, and two fatty acid tails.

Question 17

Which of the following molecules would most easily cross a pure phospholipid bilayer without the help of a protein?

Accepted Answer

A small, nonpolar molecule like $$O_2$$

Question 18

Which process is responsible for the movement of water across a cell membrane?

Accepted Answer

Osmosis

Question 19

Which of the following best explains why saturated fatty acid tails decrease membrane fluidity?

Accepted Answer

They allow for more van der Waals interactions, leading to tighter packing.

Question 20

Which of the following is a correct statement about the role of membrane proteins?

Accepted Answer

They regulate the transport of substances across the membrane.

Lipids, Membranes, and the First Cells: Structure and Function

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