Structure:
- An example of the quaternary structure
- Basic unit= iron containing haem surrounded by a polypeptide
- Haemoglobin contains 4 polypeptides (2 a-globin, 2 B-globin)
- Spherical
Structure related to function:
- Hydrophillic R-groups on the outside of the globin molecule, makes it soluble
- Oxygen binds reversibly with the iron atoms of the haem group
- 4 oxygen molecules can be carried by a haemoglobin molecule
Collagen
Structure:
- An example of a fibrous protein
- Has high tensile strength
- Contains 3 polypeptide chains (triple helix)
- H-bonds between strands and some covalent
- Every 3rd amino acid=glycine (allows the strands to be very close)
Collagen fibril:
- Covalent cross-links between carboxyl end of one molecule an amine group of another.
- Collagen fibrils are grouped together to form a fibre
