2.3.c Describe the molecular structure of haemoglobin as an example of a globular protein, and of collagen as an example of a fibrous protein and relate these structures to their functions (The importance of iron in the haemoglobin molecule should be emphasised. A haemoglobin molecule is composed of two alpha (α) chains and two beta (β) chains, although when describing the chains the terms α-globin and β-globin may be used. There should be a distinction between collagen molecules and collagen fibres).
- Fibrous proteins are present in the skin, bones, teeth, cartilage and walls of blood vessels.
- It is an important structural protein.
The above image shows the structure of a fibrous protein.
- Collagen has a structure with three polypeptide chains that are held together by hydrogen and covalent bonds.
- Each polypeptide chain are wound around each other, in a triple helix (or like a rope).
- Every third amino acid is a glycine.
- Collagen molecules linked to each other by cross-links between side chains of amino acids, which forms fibrils.
- Groups of fibrils make up collagen fibre.
The diagram shows how three polypeptide chains make one collage molecule, and how many collagen molecules make collagen fibrils.
Well done my friend! Onwards we go! 🙌
- Cornell, B. Fibrous vs Globular Proteins. Retrieved from https://ib.bioninja.com.au/standard-level/topic-2-molecular-biology/24-proteins/fibrous-vs-globular-protein.html
- Jones, M., & Parkin, M. (2018). Cambridge International AS and A Level Biology. Cambridge: Cambridge University Press.