Enzymes

This deck contains content from 3.1.4.2 Enzymes

What type of protein are enzymes?

Globular proteins

What is an active site?

The part of the enzyme where a substrate molecule will bind.

What are the active site and substrate?

Complimentary to one another

What are the two models relating to how enzymes work?

• Lock & Key

• Induced Fit

How many reactions can one enzyme catalyse?

One, as only one complementary substrate will bind with the active site

What is the shape of the active site determined by?

The enzyme’s tertiary structure

What factors can denature and enzymes active site?

• pH

• Temperature

• non-competitive inhibitors

What can mutations in a specific gene cause?

A change in the tertiary structure of the enzyme and, therefore, the active site

What do enzymes do?

Catalyse metabolic reactions

How do enzymes perform their function?

By lowering activation energy

Are enzymes used up in a reaction?

No

What is activation energy?

The amount of energy needed to get the reaction started

How do enzymes work in condensation?

The substrate being attached to the active site holds them close together, so any repulsion between the molecules is reduced, so they bond easier

How do enzymes work in hydrolysis?

The substrate binding with the active site puts strain on the bonds within the substrate, so the substrate breaks easier

What is the induced fit model of enzyme action?

1. Before the reaction, the shape of the active site isn’t complementary to the substrate, so it won’t fit

2. The shape of the active site alters as the substrate binds

3. This is caused by the bending of the hydrogen bonds in the active site

4. Enzyme-substrate complex forms

Which model of enzyme action is better?

Induced fit

How does temperature affect enzyme action?

• At low temperatures, there are fewer successful collisions due to less kinetic energy, and the energy not being high enough to meet the activation energy

• As temperature increases, there are more successful collisions

• Then we reach the optimum temperature

• Finally, above the optimum temperature, the active site becomes denatured, so the substrate and active site are no longer complementary, so there is no enzyme-substrate complexes being formed

How does pH affect enzyme activity?

• At extreme pH’s (high/low) the enzymes are denatured, so no enzyme-substrate complexes form.

• At the optimum pH more enzyme-substrate complexes form.

How does substrate concentration affect enzyme action?

• As the amount of substrate increases up to a certain point, there will be more enzyme-substrate complexes formed

• Then we reach the point of active site saturation

• As all active sites are saturated, there is no further increase in the number of enzyme-substrate complexes formed

How does enzyme concentration affect enzyme activity?

• There is a linear increase, as more active sites are available for the substrate to bind to

• This linear increase will continue so long as there is enough substrate that can bind

What are the two types of inhibitors?

• Competitive

• Non-competitive

How does a competitive inhibitor work?

It has a similar shape to the substrate and will compete with the substrate to bind to the active site, reducing the number of enzyme-substrate complexes formed

How does a non-competitive inhibitor work?

It binds away from the active site, causing the hydrogen bonds in the active site to break/alter, denaturing the active site, so no enzyme-substrate complexes form

What is the equation for the formula of the pH of a solution?

pH = —log₁₀ [H⁺]