Q: Which of the following equations best represents the movement of ions across a membrane by the Na+/K+ ATPase pump?

$$3 \mathrm{Na}^+_{\text{in}} + 2 \mathrm{K}^+_{\text{out}} + \mathrm{ATP} \rightarrow 3 \mathrm{Na}^+_{\text{out}} + 2 \mathrm{K}^+_{\text{in}} + \mathrm{ADP} + \mathrm{P}_i$$

Question 1

Which of the following best explains why biological membranes act as effective permeability barriers?

Accepted Answer

Their interior is hydrophobic, preventing the free passage of most polar molecules.

Question 2

A researcher observes that a certain membrane protein is easily removed from the membrane by changing the pH or ionic strength of the solution. What type of membrane protein is this most likely to be?

Accepted Answer

Peripheral membrane protein

Question 3

Which class of membrane lipids is most responsible for the amphipathic nature of the lipid bilayer?

Accepted Answer

Phospholipids

Question 4

A mutation causes the fatty acid tails of membrane phospholipids to become fully saturated and longer than normal. What is the most likely effect on membrane fluidity?

Accepted Answer

Membrane fluidity will decrease.

Question 5

Which of the following best describes the function of transmembrane proteins in cell membranes?

Accepted Answer

They span the lipid bilayer and often function as channels or transporters for specific molecules.

Question 6

Which of the following equations best represents the movement of ions across a membrane by the Na+/K+ ATPase pump?

Accepted Answer

$$3 \mathrm{Na}^+_{	ext{in}} + 2 \mathrm{K}^+_{	ext{out}} + \mathrm{ATP} ightarrow 3 \mathrm{Na}^+_{	ext{out}} + 2 \mathrm{K}^+_{	ext{in}} + \mathrm{ADP} + \mathrm{P}_i$$

Question 7

A cell is placed in a solution containing a high concentration of a small, nonpolar molecule. Which of the following is most likely to occur?

Accepted Answer

The molecule will diffuse freely across the membrane down its concentration gradient.

Question 8

Which of the following statements about membrane asymmetry is correct?

Accepted Answer

Most lipids are distributed unequally between the two monolayers of the bilayer.

Question 9

Which of the following membrane components is most directly involved in cell-cell recognition, such as in the ABO blood group system?

Accepted Answer

Glycolipids

Question 10

A scientist is studying a membrane protein that is covalently linked to glycosylphosphatidylinositol (GPI). What type of membrane protein is this?

Accepted Answer

Lipid-anchored membrane protein

Question 11

Which of the following changes would most likely increase the fluidity of a cell membrane?

Accepted Answer

Increasing the proportion of phospholipids with cis-unsaturated fatty acid tails

Question 12

Which of the following best describes the role of membrane proteins in signal transduction?

Accepted Answer

They act as receptors that bind external signal molecules and initiate cellular responses.

Question 13

Which of the following is a function of the glycocalyx on the cell surface?

Accepted Answer

Protection, cell recognition, and regulation of permeability

Question 14

A membrane protein is found to cross the lipid bilayer seven times, forming a pore. What is the most likely function of this protein?

Accepted Answer

Channel protein

Question 15

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

Accepted Answer

Facilitated diffusion moves molecules down their concentration gradient without energy input, while active transport moves molecules against their gradient using energy.

Question 16

Which of the following is a real-world example of a membrane protein acting as an enzyme?

Accepted Answer

Cytochrome c oxidase in the mitochondrial inner membrane catalyzing electron transfer during cellular respiration

Question 17

Which of the following best explains why some membrane proteins are immobile within the membrane?

Accepted Answer

They are anchored to cytoskeletal or protein complexes.

Question 18

A cell is exposed to a hormone that binds to a receptor on its surface. Which process is most directly initiated by this event?

Accepted Answer

Signal transduction

Question 19

Which of the following best describes the function of tight junctions in animal cells?

Accepted Answer

They form seals that block the passage of fluids between cells.

Cell Membranes: Structure, Function, and Chemistry (Becker's World of the Cell, Chapter 7 Study Notes)

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