Question 1

Which of the following best describes the role of the sodium-potassium pump in animal cells?

Accepted Answer

It uses ATP to move Na$$^+$$ out of the cell and K$$^+$$ into the cell against their concentration gradients.

Question 2

A reaction has a negative free energy change ($$\Delta G \u003c 0) $$but does not proceed at a measurable rate at room temperature. What is the most likely explanation?

Accepted Answer

The activation energy ($$E_a) is $$too high for the reaction to proceed rapidly.

Question 3

Which of the following statements about ATP hydrolysis is correct?

Accepted Answer

ATP hydrolysis is exergonic because the products (ADP and P$$_i) $$are more stable and better solvated than ATP.

Question 4

Which process is illustrated by the movement of H$$^+$$ ions out of a cell via a proton pump, followed by the cotransport of sucrose with H$$^+$$ back into the cell?

Accepted Answer

Cotransport (secondary active transport)

Question 5

What is the main difference between competitive and noncompetitive enzyme inhibitors?

Accepted Answer

Competitive inhibitors can be overcome by increasing substrate concentration, while noncompetitive inhibitors cannot.

Question 6

Which of the following best explains why a living cell must remain an open system?

Accepted Answer

To allow continuous input of food and removal of waste, preventing equilibrium ($$\Delta G = 0) $$and cell death.

Question 7

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

Accepted Answer

The end product of a pathway binding to an allosteric site on the first enzyme, reducing its activity.

Question 8

Which of the following statements about enzymes is FALSE?

Accepted Answer

Enzymes change the free energy change ($$\Delta G) of a $$reaction.

Question 9

Which type of bulk transport is responsible for the uptake of cholesterol into animal cells?

Accepted Answer

Receptor-mediated endocytosis

Question 10

A cell is placed in a solution with a high concentration of solute. What will happen to the cell due to osmosis?

Accepted Answer

Water will move out of the cell, causing it to shrink.

Question 11

Which of the following best describes the process of exocytosis?

Accepted Answer

A vesicle fuses with the plasma membrane, releasing its contents outside the cell.

Question 12

Which of the following is true about the hydrolysis of ATP?

Accepted Answer

It is an exergonic reaction with $$\Delta G \u003c 0.$$

Question 13

Which of the following best explains why enzymes are specific for their substrates?

Accepted Answer

The active site of the enzyme has a unique shape and chemical environment that fits only specific substrates.

Question 14

Which of the following is a correct statement about catabolic and anabolic pathways?

Accepted Answer

Catabolic pathways break down molecules and release energy, while anabolic pathways build molecules and require energy.

Question 15

A scientist adds a competitive inhibitor to an enzyme-catalyzed reaction. What will happen if the substrate concentration is greatly increased?

Accepted Answer

The reaction rate will return to normal as the substrate outcompetes the inhibitor.

Question 16

Which of the following best describes the effect of temperature on enzyme activity?

Accepted Answer

Enzyme activity increases with temperature up to an optimum, then decreases as the enzyme denatures.

Question 17

Which of the following is an example of energy coupling in cells?

Accepted Answer

The hydrolysis of ATP is used to drive the synthesis of glutamine from glutamic acid and ammonia.

Question 18

Which of the following statements about allosteric regulation is correct?

Accepted Answer

Allosteric regulation involves binding at a site other than the active site, changing the enzyme's shape and activity.

Question 19

Which of the following best explains why a campfire, a bowl of sugar, and your cells all involve the same net reaction but proceed at different rates?

Accepted Answer

The activation energy ($$E_a) $$barrier is overcome differently: heat in a fire, enzymes in cells, and not at all in a sugar bowl.

Metabolism and Enzymes: Direction, Currency, Speed, and Control

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