$$\text{Water moves from a region of lower solute concentration to a region of higher solute concentration}$$

Question 1

Which property of the plasma membrane allows it to regulate the movement of substances into and out of the cell?

Accepted Answer

Selective permeability

Question 2

Phospholipids are described as amphipathic molecules. What does 'amphipathic' mean in this context?

Accepted Answer

They contain both hydrophobic and hydrophilic regions

Question 3

According to the fluid mosaic model, which statement best describes the arrangement of proteins in the plasma membrane?

Accepted Answer

Proteins are embedded within the lipid bilayer, with hydrophilic regions exposed to water and hydrophobic regions buried in the membrane

Question 4

Which type of movement is most common for phospholipids within the plasma membrane?

Accepted Answer

Lateral movement within the bilayer

Question 5

A cell is placed in a solution and begins to lose water. What type of solution is the cell in?

Accepted Answer

Hypertonic solution

Question 6

Which of the following molecules can most easily cross the plasma membrane without the help of transport proteins?

Accepted Answer

Nonpolar molecules such as $$CO_2$$

Question 7

What is the main function of aquaporins in the plasma membrane?

Accepted Answer

Facilitate the diffusion of water across the membrane

Question 8

Which of the following statements about membrane fluidity is correct?

Accepted Answer

Membranes rich in unsaturated fatty acids are more fluid than those rich in saturated fatty acids

Question 9

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

Accepted Answer

Active transport

Question 10

A red blood cell is placed in pure water. What will happen to the cell, and why?

Accepted Answer

It will swell and possibly burst because water enters the cell due to the hypotonic environment

Question 11

Which of the following best describes the function of the sodium-potassium pump?

Accepted Answer

It uses ATP to move $$Na^+$$ out of the cell and $$K^+$$ into the cell, maintaining membrane potential

Question 12

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

Accepted Answer

DNA replication

Question 13

What is the main difference between channel proteins and carrier proteins?

Accepted Answer

Channel proteins provide corridors for molecules to pass, while carrier proteins change shape to shuttle molecules across the membrane

Question 14

Which equation best represents the movement of water during osmosis?

Accepted Answer

$$	ext{Water moves from a region of lower solute concentration to a region of higher solute concentration}$$

Question 15

Which of the following statements about facilitated diffusion is true?

Accepted Answer

It is a passive process that uses transport proteins to move substances down their concentration gradient

Question 16

Which type of membrane protein is most likely to be restricted in its movement due to attachment to the cytoskeleton?

Accepted Answer

Integral membrane protein

Question 17

Which of the following best explains why cholesterol is important for membrane fluidity?

Accepted Answer

It restrains movement of phospholipids at warm temperatures and prevents tight packing at cool temperatures

Question 18

Which process describes the movement of large molecules such as proteins out of the cell?

Accepted Answer

Exocytosis

Question 19

What is the main electrogenic pump in plant cells?

Accepted Answer

Proton pump

Question 20

A Paramecium living in a freshwater pond uses a contractile vacuole to maintain water balance. What is the main reason for this adaptation?

Accepted Answer

The Paramecium is hypertonic to its environment and must expel excess water entering by osmosis

Structure and Function of the Plasma Membrane

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