A - 6 - Enzymes Flashcards
What is an enzyme?
A protein that speeds up the rate of a chemical reaction
What is an active site?
The site of an enzyme where a substate molecule binds. It has a specific shape
Why are enzymes highly specific?
It is due to their territory structure
What is the activation energy?
The energy that needs to be supplied before a chemical reaction will start
What is an intracellular reaction?
A reaction that takes place inside a cell
What is an extracellular Reaction?
A reaction that takes place outside of a cell
How does the structure of an enzyme relate to its function?
- Has a tertiary structure
- Usually roughly spherical I shape due to the tight folding of the polypeptide chains
- Soluble and often have roles in metabolism
- Some enzymes break down large food molecules
- Other enzymes help to synthesise larger molecules
How is the activation energy often provided to an enzyme?
It is usually in the form of heat
How do enzymes speed up a reaction?
They lower the amount of activation energy that’s needed, which often makes reactions happen at a lower temperature than they could without an enzyme
What is an enzyme-substrate complex?
The intermediate formed when a substate molecule binds to the active site of an enzyme
Give two reasons why an enzyme substate complex lowers the activation energy
1 - If two substate molecules need to be joined, being attached to the enzyme holds them close together, reducing any repulsion between the molecules so they can bond more easily
2 - If the enzyme is catalysing a breakdown reaction, fitting into the active site puts a strain on bonds in the substrate, so the substrate molecule breaks up more easily
What are the two models of enzyme action?
- The lock and key model
- The induced fit model
Describe the lock and key model of enzyme action
The substrate fits into the enzyme, as the enzyme and the active site have a complimentary shape
Describe the induces fit model of enzyme action
The substrate doesn’t have to fit the shape of the active site, it has to change the shape of the active site in the right way so that it fits.
