Models

Question 1

What are the 2 main models for enzyme action?

Answer 1

Lock and key model
Induced fit model

Question 2

Describe the lock and key model

Answer 2

Substrate molecule fits into the active site of the enzyme molecule like a key fitting into a lock as they are complementary shapes
Forms the enzyme substrate complex
Product is formed and as it no longer fits into the active site it is released
Model explains why enzymes are very specific

Question 3

Describe the induced fit model

Answer 3

Substrate and the active site of the enzyme are not complementary shape
When a substrate molecule binds to the active site, the active site changes shape and fits itself around the substrate
Places a strain on the substrate molecule and distorts a particular bond, lowering the activation energy required to break the bond
Products are formed and leave the active site which then returns to its original shape

Question 4

Describe the enzyme lysozyme in terms of the induced fit model

Answer 4

Lysozyme’s active site is not perfectly complementary to the substrate
Lysozyme’s active site changes shape to fit the substrate
This lowers the activation energy needed for the reaction to occur
The products are released and the lysozyme’s active site returns to its original shape

Question 5

What is the function of the enzyme lysozyme?

Answer 5

Helps to kill bacteria by catalysing the hydrolysis of sugars in the peptidoglycan cell walls

Question 6

What happens when lysozyme catalyses the hydrolysis of sugars in the peptidoglycan cell walls?

Answer 6

Cell walls are weakened, the bacteria absorb water by osmosis and burst

Question 7

Where is lysozyme present?

Answer 7

Present in many secretions such as tears, saliva, human milk and inside lysosomes