Biology Topic Practice

The Lock and Key Theory

The lock and key theory is a simplified model used to explain how enzymes show high specificity for their substrates.

Can you describe the active site's role in one sentence?

What is The Lock and Key Theory?

"The lock and key theory is a model explaining the specificity of enzyme-substrate complexes."

Question 1

Why are enzymes described as biological catalysts?

Question 2

Why is an enzyme specific to one substrate or a small group of substrates?

Question 3

Why are enzymes described as biological catalysts?

Enzyme Specificity

The substrate (key) fits into the active site (lock).

The shape of the active site is complementary to the substrate.

Chemical reactions occur while the substrate is bound.

Exam Tip

Remember the keyword "complementary" when describing how the substrate fits.

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