AP Bio Insta-Review Topic 3.4: Cellular Energy

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What is an endergonic reaction?

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An endergonic reaction is a chemical reaction that requires an input of energy, resulting in a positive change in Gibbs free energy (ΔG > 0) and is nonspontaneous.

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What does the second law of thermodynamics state?

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The second law of thermodynamics states that every energy transfer or transformation increases the entropy of the universe.

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What is an exergonic reaction?

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An exergonic reaction is a chemical reaction that releases energy, resulting in a negative change in Gibbs free energy (ΔG < 0) and is spontaneous.

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What does the first law of thermodynamics state?

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The first law of thermodynamics states that energy cannot be created or destroyed, only transferred or transformed.

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What is the significance of Gibbs free energy (ΔG)?

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Gibbs free energy (ΔG) indicates the spontaneity of a reaction; a negative ΔG means the reaction is spontaneous, while a positive ΔG means it is nonspontaneous.

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Define entropy in the context of thermodynamics.

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Entropy is a measure of the disorder or randomness in a system; higher entropy indicates greater disorder.

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What is the relationship between exergonic reactions and spontaneity?

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Exergonic reactions are spontaneous because they release energy, leading to a decrease in Gibbs free energy (ΔG < 0).

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What is the relationship between endergonic reactions and spontaneity?

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Endergonic reactions are nonspontaneous because they require an input of energy, resulting in a positive Gibbs free energy (ΔG > 0).

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Provide an example of an endergonic reaction.

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Photosynthesis is an example of an endergonic reaction, where plants absorb energy from sunlight to convert carbon dioxide and water into glucose.

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Provide an example of an exergonic reaction.

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Cellular respiration is an example of an exergonic reaction, where glucose is broken down to release energy.