Activation energy and energy profiles
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Flip to reveal answersWhat is activation energy (Eₐ)?
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All 12 Flashcards — Activation energy and energy profiles
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Question
What is activation energy (Eₐ)?
Answer
The **minimum energy** the reactants must have for a reaction to **start**.
Question
On an energy profile, where is the activation energy shown?
Answer
The **height from the reactants level up to the peak** of the curve.
Question
What is an energy profile?
Answer
A graph showing how the **energy of a reacting system changes** as the reaction goes from reactants to products.
Question
How does an enzyme affect the activation energy?
Answer
It **lowers** the activation energy.
Question
Why does lowering the activation energy speed up a reaction?
Answer
A **smaller barrier** means **more reactant particles have enough energy** to react, so the reaction goes faster.
Question
Does an enzyme change the energy of the reactants or products?
Answer
**No** — it lowers only the activation energy; the reactants and products stay at the **same energy levels**.
Question
On a with/without-enzyme graph, which curve is the catalysed one?
Answer
The one with the **lower peak / smaller activation-energy barrier**.
Question
What does the left-hand starting level of an energy profile show?
Answer
The energy of the **reactants** (substrate).
Question
What does the right-hand finishing level of an energy profile show?
Answer
The energy of the **products**.
Question
How do you read the energy released off an energy profile?
Answer
The **drop from the reactants level down to the products level**.
Question
Is an enzyme used up in the reaction it speeds up?
Answer
**No** — an enzyme is a catalyst; it is **not used up** and can be used again.
Question
What is the peak of the curve on an energy profile called?
Answer
The **transition state** — the most unstable, highest-energy point of the reaction.
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Topic 3.1 hub
Enzymes and metabolism
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