Question 1

What does a negative ΔG value indicate about a chemical reaction?

Accepted Answer

A negative ΔG indicates the reaction is exergonic and will proceed spontaneously, releasing free energy that can do work.

Question 2

What is the First Law of Thermodynamics and how does it apply to living organisms?

Accepted Answer

Energy cannot be created or destroyed, only converted from one form to another. Living organisms transform energy (e.g., light to chemical, chemical to kinetic) but cannot create it from nothing.

Question 3

Why must cells continuously produce ATP rather than storing large quantities of it?

Accepted Answer

ATP is unstable and cannot be stored long-term; cells maintain a small pool that is rapidly recycled because the high-energy phosphate bonds are quickly hydrolyzed in metabolic reactions.

Question 4

How does coupling an exergonic reaction to an endergonic reaction allow the endergonic reaction to proceed?

Accepted Answer

The free energy released by the exergonic reaction provides the energy needed for the endergonic reaction. If the combined ΔG is negative, the overall coupled process is spontaneous.

Question 5

Which bond in ATP releases the most usable free energy upon hydrolysis, and approximately how much energy is released?

Accepted Answer

The terminal (gamma) phosphoanhydride bond releases approximately 7.3 kcal/mol (30.5 kJ/mol) of free energy when hydrolyzed to ADP and inorganic phosphate.

AP Biology: Energy & Metabolism

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