Proteins

Question 1

What is a dipeptide?

Answer 1

Two amino acids joined together by peptide bond in condensation reactions.

Question 2

What is a polypeptide?

Answer 2

Many amino acids joined by peptide bonds in condensation reactions.`

Question 3

Describe the structure of proteins.

Answer 3

1. Primary structure is the specific sequence of amino acids in the polypeptide chain held together by peptide bonds in condensation reactions.
2. Secondary structure folds into alpha helix or beta pleated sheets held together by hydrogen bonds.
3. Tertiary structure is the specific 3D shape held together by hydrogen bonds, ionic bonds and disulphide bridges between R-groups.
4. Quaternary structure is where more than one polypeptide chain joins together.

Question 4

What is a fibrous protein?

Answer 4

• insoluble as their external r-groups are non-polar.
• simple tertiary structure
• secondary structure consisting of long parallel polypeptide chains forming fibres or sheets

Eg. Keratin, collagen

Question 5

What is a globular protein?

Answer 5

• highly folded or coiled polypeptide chains
• compact, complex tertiary structure
• soluble

Eg. Antibodies, enzymes