Lock and key theory

Question 1

Why was the lock and key theory introduced

Answer 1

• To try and explain the specificity of enzyme reactions
  
  • i.e. Why enzymes only work with 1 substrate

Question 2

What is a substrate

Answer 2

A substrate is the structure which an enzyme bonds with, to catalyze a reaction.

Question 3

Is an enzyme larger or smaller than a substrate

Answer 3

Larger

Question 4

What is the active site

Answer 4

• The area of the enzyme which bonds with the substrate

Question 5

What is the lock and key theory

Answer 5

• The substrate (Key)
• Bonds with the enzymes active site (lock)
• To form a temporary structure called an enzyme substrate complex where the reaction takes place
• Once the reaction occurs the product is rejected
• The enzyme returns to its normal state to repeat the reaction as required.

Question 6

How does a reaction occur

Answer 6

• The substrate (Key)
• Bonds with the enzymes active site (lock)
• To form a temporary structure called an enzyme substrate complex where the reaction takes place
• Once the reaction occurs the product is rejected
• The enzyme returns to its normal state to repeat the reaction as required.

Question 7

Important…

Is the reason the substrate can fit into the active site because they have the same shape

Answer 7

• No they are not the same shape!
• The substrate acts as a (key) which can fit into the enzymes active site (The lock)

Question 8

What is the name given when the substrate (the key) and the enzymes active site (the lock) fit each other

Answer 8

• Complimentary

Question 10

What does the lock and key theory help to explain

Answer 10

• The lock and key theory explains many of the properties of enzymes
  
  • e.g. Specificity, the reason why an enzyme reacts with just one type of substrate

Question 11

The lock and key theory has been updated, what is the name given to this new theory

Answer 11

• Induced fit theory

Question 12

What does the induced fit theory suggest

Answer 12

• The induced fit theory suggests that the enzyme may not exactly correspond to its substrate
• It may mold itself around the substrate to enable a reaction to occur
• Then after the reaction occurs the products are repelled
• and the enzyme returns to its relaxed state to bond with other substrates later.