Basic Info

Question 0

What is the active site of an enzyme?

Answer 0

• region where the enzyme binds to the substrate, forming an enzyme-substrate complex
• it is 3-dimensional, often a cleft or crevice of the surface of the protein

Question 1

What is an enzyme?

Answer 1

A biological catalyst
They increase the rate of a chemical reaction without being used up
They increase the rate by providing a different path for the reaction by lowering the activation energy

Question 2

How is the substrate bound to the active site of the enzyme?

Answer 2

By multiple weak interactions

• i.e. Electrostatic interactions, hydrogen bonds, van der Waals forces, hydrophobic interactions
• also in some cases by reversible covalent bonds

Question 3

What determines substrate specificity of an enzyme?

Answer 3

*the properties and spatial arrangement of had amino acid residues that form the active site.

Question 4

What are the six main groups enzymes are classified into?

Answer 4

1. Oxidoreductases
2. Transferases
3. Hydrolases
4. Lyases
5. Isomerases
6. Ligases or syntheses

Question 5

What does an oxidoreductase enzyme do and give an example?

Answer 5

• transfers electrons

* example: alcohol dehydrogenase

Question 6

What does a transferase enzyme do and give an example?

Answer 6

• it transfers functional groups

* example: Hexokinase

Question 7

What does a hydrolase enzyme do and give an example?

Answer 7

• performs hydrolysis reactions

* example: Trypsin

Question 8

What do lyases do and give an example?

Answer 8

• add or remove groups to form a double bond

* example: pyruvate de carboxylase

Question 9

What do isomerases do and give an example?

Answer 9

• they transfer groups within a molecule

* example: Maleate isomerase

Question 10

What do ligases also called synthases do and give an example?

Answer 10

• bond formation coupled to ATP hydrolysis

* example: pyruvate carboxylase

Question 11

Give three ways an enzyme lowers the activation energy of a reaction.

Answer 11

• orientation
• physical strain
• chemical change

Question 12

What is an isozyme?

Answer 12

• different forms of an enzyme that catalyse the same reactions
• but they exhibit different physical or kinetic properties

Question 13

What is a cofactors?

Answer 13

• small non protein units that are needed for some enzymes to carry out their reactions
• they maybe inorganic ions i.e. Zn2+ or Fe2+, or a complex organic molecule– a coenzyme

Question 14

What is a prosthetic group?

Answer 14

A metal or coenzyme (tightly bound) covalently attached to the enzyme

Question 15

What is a holoenzyme?

Answer 15

A catalytically active enzyme together with its coenzyme or metal ion

Question 16

What is an apoenzyme?

Answer 16

The protein part of the enzyme without its cofactor

Question 17

What are the two groups cofactors are subdivided into?

Answer 17

Metals

Coenzymes- small organic molecules