Topic 8.1 - Enzymes

Question 1

Competitive inhibitory enzymes

Answer 1

Bind to the active site, preventing other substances from binding.

Question 2

Non-competitive inhibitory enzymes

Answer 2

Bind to a different part of the enzyme (this interaction is an allosteric interaction to an allosteric site) and cause the active site to change shape.

Question 3

Induced-fit model

Answer 3

Lock and key model not fully accurate as some enzymes can catalyse multiple reactions - would not be possible if enzymes are complementary to ONLY one substrate.

As substrate interacts with the enzyme, it changes conformationally to fit with the substrate and helps to reduce the Eₐ by interacting with the bonds in the substrate.

Question 4

Evaluating models

Answer 4

Lock and key:

✔ Explains high enzyme specificity

❌ Doesn’t explain how some enzymes can catalyse many reactions

Induced-fit:

✔ Conformational change explains how Eₐ is reduced - substrate stressed (adding pressure to break it up like snapping ie by breaking bonds) which reduces the Eₐ of the reaction.
✔ Shows that active site is not rigid

❌ Implies shape can be changed for any substrate, does not happen - often just one enzyme for one substrate