Biology Chapter 1

Question 1

Can you explain how each enzyme lowers the activation energy of the reaction it catalyses?

Answer 1

When an enzyme-substrate complex forms:

(Joining) In active site, molecules are held close together, repulsions between molecules reduces so bonds can form more easily

(Breaking down) Being in active site put strain on bonds so it breaks down more easily

Question 2

How does an enzyme’s structure relate to it’s function?

Answer 2

Due to an enzyme’s tertiary structure, they have a highly specific shape of the active site which helps them to catalyse specific reactions

Question 3

Describe how you could measure the rate of an enzyme-catalysed reaction and explain the results you would expect

Answer 3

1. The formation of the products of the reaction. This would increase over time and then plateau
2. Disappearance of the substrate. This would decrease over time

Question 4

Describe the induced fit model of enzyme action

Answer 4

As the substrate molecule approaches the active site of the enzyme the enzyme molecule changes shape slightly as the substrate molecule binds with its active site. An enzyme-substrate complex is formed. Then the product molecule is formed and the enzyme molecule resumes its original shape and the active site is free to accept another pair of substrate molecules

Question 5

Describe how models of enzyme action have changed over time

Answer 5

Lock and key model:

Lock = enzyme 
Key = substrate

Limitation = the enzyme is considered to be a rigid structure