AP Biology : Cellular energetics
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Example Questions
Example Question #1 : Understand Atp Coupling
Given the hydrolysis of 1 mole of 
Given that the hydrolysis of 1 mole of ATP has delta G of 
Example Question #2 : Understand Atp Coupling
ATP coupling describes the process through which hydrolysis of ATP can drive a __ reaction
thermodynamically unfavorable
spontaneous
exothermic
thermodynamically favorable
thermodynamically unfavorable
ATP coupling is the process where hydrolysis of ATP (a thermodynamically favorable, negative delta G, or spontaneous reaction) is coupled with a thermodynamically unfavorable reaction (a reaction that cannot proceed without energy input).
Example Question #3 : Understand Atp Coupling
Which of the following is an endergonic reaction?
Na+/K+ pump
Cellular respiration
Hydrolysis of ATP
Catabolism
Na+/K+ pump
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.
Example Question #4 : Understand Atp Coupling
Which is true of an exergonic reaction?
Energy is required
The reaction will not occur spontaneously
Energy is released
The reaction will always be endothermic
Energy is released
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.
Example Question #5 : Understand Atp Coupling
ATP phosphorylation (ADP+ Pi-> ATP+ H2O) is what type of reaction?
catabolic
exergonic
endergonic
spontaneous
endergonic
ATP hydrolysis is exergonic. ATP phosphorylation is the reverse of ATP hydrolysis, and thus is endergonic.
Example Question #6 : Understand Atp Coupling
If the reaction for ATP hydrolysis 
Through ATP coupling, the hydrolysis of ATP can allow the second, thermodynamically unfavorable reaction to proceed. 
Example Question #1 : Understand Structure And Importance Of Atp
Which is NOT a reason that the phosphoanhydride bonds of ATP are high energy?
Repulsion of positively charged phosphate and negatively charged oxygen
Large mass of phosphate provides significant energy when combusted
Entropy is increased when bonds are broken
Resonance stabilization of products of ATP hydrolysis
Large mass of phosphate provides significant energy when combusted
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.
Example Question #2 : Understand Structure And Importance Of Atp
Which is not part of an ATP molecule?
ribose sugar
alpha phosphate, beta phosphate, and gamma phosphate groups
adenine
threonine
threonine
ATP consists of 3 phosphate groups, a ribose sugar, and adenine.
Example Question #3 : Cellular Energetics
Which is true of an ATP molecule?
It is used for long-term energy storage
When hydrolyzed, delta G> 0
When hydrolyzed, a phosphoanhydride bond is formed
It is unstable
It is unstable
ATP is unstable; there is close proximity of positively charged phosphate and negatively charged oxygen; these charges repel. When hydrolyzed, delta G is <0 (exergonic). ATP is not used for long term-energy storage, as it is unstable. When hydrolyzed, a phosphoanhydride bond is broken.
Example Question #3 : Understand Structure And Importance Of Atp
Which is true of ADP
It contains 3 phosphate groups
It contains more energy than ATP
It contains 2 phosphate groups
ATP is produced when ADP is broken down
It contains 2 phosphate groups
When ATP is hydrolyzed and a phosphoanhydride bond is broken, ADP and a phosphate are the products. ADP then has 2 phosphate groups.
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