Enzyme specificity, the active site and activation energy

Overview

Recall questions on the lock and key and induced fit models, activation energy, and intracellular against extracellular enzymes.

What you need to know

Answer each one before you reveal it.

Questions from this subtopic

Each one with the model answer underneath.

1. 1

   Describe the structural feature of an enzyme that allows it to bind with its substrate.

   Model answer

   Enzymes have a specific three-dimensional shape that includes an active site, which is complementary in shape to the substrate molecule.

2. 2

   Why can an enzyme only catalyse a specific reaction?

   Model answer

   Only substrates with a complementary shape can fit into the active site, forming an enzyme-substrate complex, so each enzyme is specific to particular substrates.

3. 3

   What is an enzyme-substrate complex?

   Model answer

   A temporary structure formed when a substrate molecule binds to the active site of an enzyme.

4. 4

   Describe the lock and key model of enzyme action.

   Model answer

   The lock and key model proposes that the substrate fits exactly into the active site like a key into a lock, with no change in shape of the active site.

5. 5

   How does the induced fit model differ from the lock and key model?

   Model answer

   In the induced fit model, the active site changes shape slightly as the substrate binds, moulding around the substrate to form a more precise fit, rather than being a rigid exact match.

6. 6

   What happens to the shape of the active site when a substrate binds according to the induced fit model?

   Model answer

   The active site changes shape slightly, moulding around the substrate to form a more precise fit.

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