AP Biology : AP Biology

Study concepts, example questions & explanations for AP Biology

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Example Questions

Example Question #2561 : Ap Biology

Which is NOT true of the lock and key model of enzyme substrate bonding?

Possible Answers:

The enzyme does not have a separate catalytic group

There is a transition state during which the shape of the active site changes to better fit the substrate

The active site fits perfectly with the substrate

 

The active site is static

Correct answer:

There is a transition state during which the shape of the active site changes to better fit the substrate

Explanation:

 The lock and key model states that the active site of an enzyme precisely fits a specific substrate. The induced fit model states that the active site of an enzyme will undergo a conformational change when binding a substrate, to improve the fit. The induced fit model does not account for a transition state during which the shape of the active site changes to better fit the substrate.

Example Question #2562 : Ap Biology

How do enzymes speed up a reaction?

Possible Answers:

Decrease yield of reaction

Stabilization of transition state, increasing activation energy

Increase enthalpy of reaction

Stabilization of transition state, lowering activation energy

Correct answer:

Stabilization of transition state, lowering activation energy

Explanation:

 Enzymes speed up reactions through lowering the activation energy, of the energy needed to break bonds of reactants. The activation energy is lowered through stabilizing the transition state; the active site of the enzyme better fits the substrate, allowing bonds to more readily be broken, requiring less energy.

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