Proteins

Question 1

Proteins

Answer 1

• has C, H, O2 and nitrogen, some have sulphur and phosphorus
• made of amino acids

Question 2

Structure of amino acids

Answer 2

carbon has:
- amino group NH2 (N-terminal)
- a carboxyl group COOH (C-terminal
- a hydrogen atom - H
- the R group - R (the variable)

Question 3

Formation of a peptide bond

Answer 3

• the amino group reacts with the carboxyl group of an amino acid, condensation reaction
• forms a peptide bond

Question 4

Fibrous protein

Answer 4

• long thin molecules, so insoluble in water
• polypeptide in parallel chains, cross-links form long fibres - e.g. keratin in hair
• strong and tough
• single fibre has three identical polypeptide chains twisted around, hydrogen bonds make it stable

Question 5

Globular protein

Answer 5

• compact
• folded into spherical protein, soluble in water and have many functions
• haemoglobin is a globular protein
  - four folded polypeptide chains with iron-group, haem at the centre