GCSE Biology: Enzymes

Biological catalysts, the active site, lock-and-key, and denaturing.

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What is a catalyst?
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A substance that speeds up the rate of a reaction without being used up itself.
Enzymes are ?.
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biological catalysts
What type of molecules are enzymes?
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Large protein molecules.
The region of an enzyme where the substrate binds is called the ?.
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active site
Why are enzymes described as specific?
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Because the active site has a specific shape that fits only one type of substrate.
The ? model explains how enzymes and substrates fit together.
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lock-and-key
Why does enzyme reaction rate increase with temperature initially?
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Because the molecules move faster and collide more often.
What happens to an enzyme when the temperature gets too high?
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The active site changes shape and the enzyme becomes denatured, so it can no longer catalyse the reaction.
How does pH affect enzymes?
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A pH that is too high or too low will denature the enzyme by changing the shape of the active site. Each enzyme has an optimum pH at which it works best.
Do stomach enzymes work best in acidic or alkaline conditions?
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Acidic conditions.
Do small intestine enzymes work best in acidic or alkaline conditions?
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Alkaline conditions.

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