Question 1

Which of the following best describes an amphipathic molecule, such as a phospholipid in the cell membrane?

Accepted Answer

It has both hydrophilic and hydrophobic regions.

Question 2

A scientist observes that a cell membrane remains flexible at low temperatures. Which component is most responsible for this property?

Accepted Answer

Cholesterol, because it prevents phospholipids from packing too tightly together.

Question 3

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

Accepted Answer

Their kinks prevent phospholipids from packing tightly, maintaining fluidity.

Question 4

Which of the following is the main function of carbohydrates in the cell membrane?

Accepted Answer

Cell recognition and communication.

Question 5

An animal cell is placed in a hypotonic solution. What is the most likely outcome?

Accepted Answer

The cell will swell as water enters.

Question 6

Which of the following best describes the difference between passive and active transport across a cell membrane?

Accepted Answer

Passive transport moves substances down their concentration gradient without energy; active transport moves substances against their gradient using energy.

Question 7

Arrange the following molecules in order of their likelihood to diffuse across the cell membrane, from most to least readily: small nonpolar molecules, large polar molecules, small polar molecules, ions.

Accepted Answer

Small nonpolar molecules \u003e small polar molecules \u003e large polar molecules \u003e ions

Question 8

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

Accepted Answer

It uses energy to move sodium out of the cell and potassium into the cell.

Question 9

A plant cell is placed in a hypertonic solution. What is the most likely outcome?

Accepted Answer

The cell will undergo plasmolysis as water leaves.

Question 10

Which of the following statements about integral and peripheral membrane proteins is correct?

Accepted Answer

Integral proteins are embedded within the lipid bilayer, while peripheral proteins are attached to the membrane surface.

Question 11

Which process allows a cell to selectively take in specific molecules from its environment?

Accepted Answer

Receptor-mediated endocytosis

Question 12

Which of the following best describes the difference between an anabolic and a catabolic pathway?

Accepted Answer

Anabolic pathways build large molecules from smaller ones and are endergonic; catabolic pathways break down large molecules and are exergonic.

Question 13

Which of the following is true for an exergonic reaction?

Accepted Answer

It is spontaneous, $$\Delta G is $$negative, and free energy is released.

Question 14

How do enzymes speed up the rate of a chemical reaction?

Accepted Answer

They lower the activation energy required for the reaction.

Question 15

A competitive inhibitor affects an enzyme by:

Accepted Answer

Competing with the substrate for the active site.

Question 16

Which of the following best describes allosteric regulation of an enzyme?

Accepted Answer

A molecule binds to a site other than the active site, altering enzyme activity.

Question 17

Which of the following is an example of feedback inhibition?

Accepted Answer

The final product of a metabolic pathway inhibits an earlier enzyme in the pathway.

Question 18

According to the second law of thermodynamics, which of the following is true?

Accepted Answer

Every energy transfer increases the disorder (entropy) of the universe.

Question 19

A lysosomal enzyme has an optimal pH of 4.5. What would happen to its activity if the pH increased to 7?

Accepted Answer

The enzyme's activity would decrease significantly.

BIO 120 Study Guide: Membranes and Enzymes

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