Describe4 marksStandard
The table below shows some features of two proteins, haemoglobin and collagen.
| Feature | Haemoglobin | Collagen |
|---|---|---|
| Solubility in water | Soluble | Insoluble |
| Number of polypeptide chains | 4 (two α, two β) | 3 (each a long chain, about 1000 amino acids) |
| Overall shape | Roughly spherical | Long, rope-like fibres |
| Types of bonds stabilising structure | Hydrogen bonds, ionic bonds, hydrophobic interactions, disulfide bridges (in some regions) | Hydrogen bonds, cross-links between chains (covalent bonds) |
| Presence of non-protein groups | Yes – four haem groups, each with an iron ion | No |
| Function | Oxygen transport in blood | Provides tensile strength in tendons, skin, bones |
Using the information in the table and your knowledge of protein structure, describe how the structures of haemoglobin and collagen relate to their different functions.