3.7 Types of Proteins

Question 1

What are globular proteins?

Answer 1

Proteins that are compact and spherical in shape
Structure: hydrophilic R groups on outside, hydrophobic R groups inside
Soluble in water
Sometimes conjugated
Functions : enzymes, hormones, membrane proteins, antibodies, transport proteins

Question 2

What are fibrous proteins?

Answer 2

Proteins that are long and linear
Structure: limited range of amino acids often with a repetitive sequence - organised and strong
Insoluble in water
Never conjugated
Functions: structural roles, e.g. keratin and collagen

Question 3

What does conjugated mean?

Answer 3

When a protein (globular) contains a non-protein component called a prosthetic group
Prosthetic groups can be metal ions, lipids, carbohydrates or molecules derived from vitamins

Question 4

What are simple proteins?

Answer 4

Proteins without a prosthetic group

Question 5

Example of a globular protein

Answer 5

Insulin

Question 6

How does insulin being globular help with its function?

Answer 6

• Insulin is a hormone
• hormones are transported in the bloodstream which means it needs to be soluble
• globular proteins are soluble
• the structure of insulin means that it can dissolve and be transported in the blood steam

Question 7

Examples of conjugated proteins!

Answer 7

Haemoglobin

Catalase

Question 8

Examples of fibrous proteins

Answer 8

Keratin
Elastin
Collagen