Q: The Na+/K+ pump moves ions against their concentration gradients. Which equation best represents the ATP hydrolysis that powers this pump?

$$\mathrm{ATP} + \mathrm{H}_2\mathrm{O} \rightarrow \mathrm{ADP} + \mathrm{P_i} + \text{energy}$$

Question 1

Which of the following best explains why saturated fats are solid at room temperature?

Accepted Answer

Their hydrocarbon chains are straight, allowing tight packing and strong van der Waals interactions.

Question 2

A researcher is studying the permeability of artificial liposomes with different phospholipid tail lengths. Which result would you expect if the tails are shorter and more unsaturated?

Accepted Answer

The membrane will be more fluid and more permeable to small molecules.

Question 3

Which of the following statements about cholesterol in animal cell membranes is correct?

Accepted Answer

At low temperatures, cholesterol increases membrane fluidity; at high temperatures, it decreases fluidity.

Question 4

Which of the following best describes the amphipathic nature of phospholipids?

Accepted Answer

They have both hydrophilic heads and hydrophobic tails.

Question 5

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

Accepted Answer

Water will leave the cell, causing it to shrink.

Question 6

Which of the following is a function of the plasma membrane?

Accepted Answer

It acts as a selective barrier, controlling the entry and exit of substances.

Question 7

Which of the following best describes facilitated diffusion?

Accepted Answer

Movement of molecules down their concentration gradient through a membrane protein, without energy input.

Question 8

The Na+/K+ pump moves ions against their concentration gradients. Which equation best represents the ATP hydrolysis that powers this pump?

Accepted Answer

$$\mathrm{ATP} + \mathrm{H}_2\mathrm{O} ightarrow \mathrm{ADP} + \mathrm{P_i} + 	ext{energy}$$

Question 9

Which of the following is NOT a property of the plasma membrane?

Accepted Answer

It is rigid and cannot repair itself.

Question 10

A mutation causes a cell to lack functional aquaporins. What is the most likely consequence?

Accepted Answer

The cell will have a reduced rate of water transport across its membrane.

Question 11

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

Accepted Answer

Double bonds create kinks, preventing tight packing of phospholipids.

Question 12

Which of the following is an example of active transport?

Accepted Answer

The Na+/K+ pump moving Na+ out of and K+ into the cell using ATP.

Question 13

Which of the following statements about osmosis is correct?

Accepted Answer

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

Question 14

A cell in the human intestine uses a coupled transporter to import glucose. Which statement best describes this process?

Accepted Answer

The Na+ gradient established by the Na+/K+ pump is used to drive glucose uptake against its concentration gradient.

Question 15

Which of the following would most likely increase the permeability of a phospholipid bilayer to small, nonpolar molecules?

Accepted Answer

Increasing the proportion of unsaturated fatty acids in the bilayer.

Question 16

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

Accepted Answer

Membranes are composed of a fluid phospholipid bilayer with proteins embedded throughout.

Question 17

Which of the following best describes the function of carrier proteins in facilitated diffusion?

Accepted Answer

They undergo conformational changes to transport specific molecules across the membrane.

Question 18

Which of the following is a real-world consequence of a defective CFTR protein in humans?

Accepted Answer

Abnormally thick and sticky mucus in the lungs and other organs.

Question 19

Which of the following best explains why the plasma membrane is considered selectively permeable?

Accepted Answer

It allows some substances to cross more easily than others due to its lipid and protein composition.

Question 20

Which of the following would most likely decrease the fluidity of a plasma membrane at room temperature?

Accepted Answer

Increasing the proportion of saturated fatty acids in the membrane.

Membranes & Transport: Structure, Function, and Mechanisms in General Biology

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