Question 1

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

Accepted Answer

It has both a hydrophilic head and a hydrophobic tail.

Question 2

A patient is given an intravenous solution that is hypertonic relative to their red blood cells. What is the most likely outcome for the red blood cells?

Accepted Answer

They will lose water and shrink.

Question 3

Which of the following best explains how cholesterol acts as a 'fluid buffer' in animal cell membranes?

Accepted Answer

It prevents phospholipids from packing too tightly in cold temperatures and slows their movement in warm temperatures.

Question 4

Which of the following is the main function of carbohydrates attached to the cell membrane?

Accepted Answer

Cell recognition and communication.

Question 5

A scientist observes that a certain molecule crosses the cell membrane rapidly without the help of proteins. Which type of molecule is this most likely to be?

Accepted Answer

A small nonpolar molecule, such as $$\mathrm{CO_2$}.$$

Question 6

Which of the following statements about the sodium-potassium pump is correct?

Accepted Answer

It uses energy to move sodium out of the cell and potassium into the cell, both against their concentration gradients.

Question 7

Which of the following best describes the difference between channel proteins and carrier proteins?

Accepted Answer

Channel proteins form open passageways for specific substances, while carrier proteins bind and change shape to move substances across the membrane.

Question 8

Which of the following is an example of feedback inhibition in a metabolic pathway?

Accepted Answer

The final product of a pathway binds to an enzyme early in the pathway, decreasing its activity.

Question 9

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 10

Which of the following correctly orders the types of molecules from most to least likely to diffuse across a cell membrane?

Accepted Answer

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

Question 11

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

Accepted Answer

The cell will become turgid as water enters, which is optimal for plant cells.

Question 12

Which of the following best describes the difference between integral and peripheral membrane proteins?

Accepted Answer

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

Question 13

Which of the following statements about the first and second laws of thermodynamics is correct?

Accepted Answer

The first law states that energy cannot be created or destroyed, only transformed; the second law states that energy transfers increase disorder (entropy).

Question 14

Which of the following best describes how enzymes speed up chemical reactions?

Accepted Answer

They lower the activation energy required for the reaction.

Question 15

Which of the following is true about exergonic and endergonic reactions?

Accepted Answer

Exergonic reactions are spontaneous with $$\Delta G  0$$ and absorb free energy.

Question 16

Which of the following best describes the difference between competitive and noncompetitive enzyme inhibitors?

Accepted Answer

Competitive inhibitors bind to the active site; noncompetitive inhibitors bind elsewhere and change enzyme activity.

Question 17

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

Accepted Answer

A molecule binds to a site other than the active site, changing the enzyme's activity.

Question 18

Which of the following scenarios best illustrates receptor-mediated endocytosis?

Accepted Answer

A cell selectively takes in cholesterol molecules after they bind to specific membrane receptors.

Question 19

Which of the following is an example of an anabolic pathway, and is it exergonic or endergonic?

Accepted Answer

Photosynthesis, which builds glucose from $$\mathrm{CO_2$}$$ and $$\mathrm{H_2O}$$; it is endergonic.

Question 20

A lysosomal enzyme has an optimal activity at pH 4.5. What would you expect to happen to its activity at pH 7?

Accepted Answer

The enzyme's activity would decrease significantly.

BIO 120 Study Guide: Membranes and Enzymes

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