Q: A cell uses the sodium-potassium pump to maintain ion gradients. Which equation best represents the net movement of ions per ATP hydrolyzed?

$3\ Na^+_{\text{out}} : 2\ K^+_{\text{in}}$

Question 1

Which of the following best describes the Fluid Mosaic Model of the plasma membrane?

Accepted Answer

A dynamic structure with proteins and lipids that move laterally within a double layer of phospholipids.

Question 2

What is the primary function of cholesterol in the plasma membrane?

Accepted Answer

It increases membrane fluidity at high temperatures and decreases it at low temperatures.

Question 3

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 lyse as water enters the cell.

Question 4

Which of the following molecules can most easily diffuse across the plasma membrane without the help of a transport protein?

Accepted Answer

Oxygen ($O_2$)

Question 5

A cell uses the sodium-potassium pump to maintain ion gradients. Which equation best represents the net movement of ions per ATP hydrolyzed?

Accepted Answer

$3\ Na^+_{	ext{out}} : 2\ K^+_{	ext{in}}$

Question 6

Which type of membrane protein is most likely to function as a channel for passive transport?

Accepted Answer

Integral transmembrane protein

Question 7

A U-tube is divided by a membrane permeable to water and glucose but not to sucrose. Side A contains 2 M sucrose and 1 M glucose; side B contains 1 M sucrose and 2 M glucose. After equilibrium, what is the concentration of sucrose on each side?

Accepted Answer

$A = 2\ M,\ B = 1\ M$

Question 8

Which process requires energy input from the cell to move substances against their concentration gradient?

Accepted Answer

Active transport

Question 9

Which of the following is NOT a function of membrane proteins?

Accepted Answer

Synthesis of ATP in the cytoplasm

Question 10

A paramecium lives in a hypotonic pond environment. What adaptation allows it to maintain osmotic balance?

Accepted Answer

Contractile vacuole that pumps excess water out

Question 11

Which statement about membrane permeability is correct?

Accepted Answer

Small nonpolar molecules pass easily through the lipid bilayer.

Question 12

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

Accepted Answer

They create kinks that prevent tight packing of phospholipids.

Question 13

Which of the following is an example of bulk transport across the plasma membrane?

Accepted Answer

Exocytosis of insulin from pancreatic cells

Question 14

Which membrane component is responsible for cell-cell recognition, such as ABO blood group antigens?

Accepted Answer

Glycolipids and glycoproteins

Question 15

What is the main difference between peripheral and integral membrane proteins?

Accepted Answer

Integral proteins span the membrane, while peripheral proteins are attached to one side.

Question 16

Which of the following best describes facilitated diffusion?

Accepted Answer

Passive movement of molecules down their concentration gradient via a transport protein.

Question 17

During exocytosis, which of the following occurs?

Accepted Answer

Vesicles fuse with the plasma membrane and release their contents outside the cell.

Question 18

Which equation best represents the movement of water during osmosis?

Accepted Answer

$	ext{Water moves from low solute concentration to high solute concentration}$

Question 19

Which of the following is NOT a type of endocytosis?

Accepted Answer

Exocytosis

Question 20

A cell is placed in a solution and water moves out of the cell, causing it to shrink. What type of solution is this?

Accepted Answer

Hypertonic

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