Cellular energetics

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AP Biology › Cellular energetics

Questions 1 - 10
1

What is the primary energy currency for cells?

oxygen

GTP

ATP

carbohydrate

Explanation

ATP is the primary energy currency for cells. The phosphoanhydride bonds of ATP, or the bonds between phosphate molecules, are high energy. This is due to the close proximity of positively charged phosphate and negatively charged oxygen; these charges repel. Also, there is resonance stabilization of the products of ATP hydrolysis (ADP and Pi); thus ADP is more stable than ATP. Carbohydrates are broken down during glycolysis to produce ATP.

2

Which is NOT a reason that the phosphoanhydride bonds of ATP are high energy?

Repulsion of positively charged phosphate and negatively charged oxygen

Resonance stabilization of products of ATP hydrolysis

Entropy is increased when bonds are broken

Large mass of phosphate provides significant energy when combusted

Explanation

The phosphoanhydride bonds of ATP, or the bonds between phosphate molecules, are high energy. This is due to the close proximity of positively charged phosphate and negatively charged oxygen; these charges repel. Also, there is resonance stabilization of the products of ATP hydrolysis (ADP and Pi); thus ADP is more stable than ATP. Additionally, entropy is increased when ATP is hydrolyzed; the second law of thermodynamics states that the entropy of a system always increases.

3

Which is not part of an ATP molecule?

alpha phosphate, beta phosphate, and gamma phosphate groups

ribose sugar

adenine

threonine

Explanation

ATP consists of 3 phosphate groups, a ribose sugar, and adenine.

4

Which is NOT a reason that the phosphoanhydride bonds of ATP are high energy?

Repulsion of positively charged phosphate and negatively charged oxygen

Resonance stabilization of products of ATP hydrolysis

Entropy is increased when bonds are broken

Large mass of phosphate provides significant energy when combusted

Explanation

The phosphoanhydride bonds of ATP, or the bonds between phosphate molecules, are high energy. This is due to the close proximity of positively charged phosphate and negatively charged oxygen; these charges repel. Also, there is resonance stabilization of the products of ATP hydrolysis (ADP and Pi); thus ADP is more stable than ATP. Additionally, entropy is increased when ATP is hydrolyzed; the second law of thermodynamics states that the entropy of a system always increases.

5

Which is not part of an ATP molecule?

alpha phosphate, beta phosphate, and gamma phosphate groups

ribose sugar

adenine

threonine

Explanation

ATP consists of 3 phosphate groups, a ribose sugar, and adenine.

6

What is the primary energy currency for cells?

oxygen

GTP

ATP

carbohydrate

Explanation

ATP is the primary energy currency for cells. The phosphoanhydride bonds of ATP, or the bonds between phosphate molecules, are high energy. This is due to the close proximity of positively charged phosphate and negatively charged oxygen; these charges repel. Also, there is resonance stabilization of the products of ATP hydrolysis (ADP and Pi); thus ADP is more stable than ATP. Carbohydrates are broken down during glycolysis to produce ATP.

7

If the reaction for ATP hydrolysis is coupled with the reaction glucose+ sucrose-> fructose,, what is the net delta G?

Explanation

Through ATP coupling, the hydrolysis of ATP can allow the second, thermodynamically unfavorable reaction to proceed. . As the resulting delta is negative, this will be thermodynamically favorable.

8

Which of the following is an endergonic reaction?

Catabolism

Na+/K+ pump

Cellular respiration

Hydrolysis of ATP

Explanation

An endergonic reaction requires input of energy; delta G will be positive. Hydrolysis of ATP, cellular respiration, and catabolism (breakdown of a large molecule) are exergonic processes. The Na+/K+ pump is endergonic, as it requires energy. This process is coupled with ATP hydrolysis to allow it to proceed.

9

Which is true of an exergonic reaction?

The reaction will always be endothermic

The reaction will not occur spontaneously

Energy is required

Energy is released

Explanation

Exergonic reactions are reactions that release energy. Endergonic reactions are reactions that require energy to proceed. Exergonic reactions can occur spontaneously, or are thermodynamically favorable. Endergonic reactions cannot occur spontaneously, or are thermodynamically unfavorable.

10

If the reaction for ATP hydrolysis is coupled with the reaction glucose+ sucrose-> fructose,, what is the net delta G?

Explanation

Through ATP coupling, the hydrolysis of ATP can allow the second, thermodynamically unfavorable reaction to proceed. . As the resulting delta is negative, this will be thermodynamically favorable.

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