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.
![General structure of a fibrous protein. General structure of a fibrous protein.](http://custom-images.strikinglycdn.com/res/hrscywv4p/image/upload/c_limit,fl_lossy,h_9000,w_1200,f_auto,q_auto/2451083/710370_43558.jpeg)
The above image shows the structure of a fibrous protein.
COLLAGEN
- 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.
![broken image](http://custom-images.strikinglycdn.com/res/hrscywv4p/image/upload/c_limit,fl_lossy,h_9000,w_1200,f_auto,q_auto/2451083/389606_780752.png)
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! 🙌
![broken image](http://custom-images.strikinglycdn.com/res/hrscywv4p/image/upload/c_limit,fl_lossy,h_9000,w_1200,f_auto,q_60/2451083/828969_752834.gif)
References:
- 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.