Proteins In Action

Question 1

What quaternary structure?

Answer 1

Quaternary structure refers to some proteins made up of more than one polypeptide subunit joined together. Many involve two identical coming together. Examples: Haemoglobin/Insulin.

Question 2

What is the structure of Haemoglobin?

Answer 2

• • Two alpha-chains, and two beta-chains - form one Haemoglobin molecule, water-soluble globular protein.
• • Haem group responsible for colour of Haemoglobin, Fe2+.
• • One complete molecule can bind to up to four oxygen molecules.
• • Haem group not an amino acid - found in some proteins, known as prosthetic groups.

Question 3

What is the structure of collagen?

Answer 3

• • Fibrous protein, made of three integrated chains - each coil containing 1000 amino acids. Hydrogen bonds form between chains.
• • Adjacent collagen molecules form covalent bonds, called cross-links, with adjacent collagen molecules.
• • Resulting structure is a fibril. Many fibrils form a collagen fibre.
• • Functions: Artery lining, tendons for muscles to pull for movement, bones (reinforced with calcium phosphate), cartilage and connective tissues, cosmetic treatments e.g. Lip buffering.