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Proteins- Haemoglobin and Collagen
Haemoglobin has a quaternary structure made up of 4 separate polypeptide
2 identical -chains and 2 identical -chains.
Each polypeptide chain is folded/coiled into a compact
shape due to hydrophobic interactions between the
The Hydrophilic R-groups are arranged around the
outside of the molecule which allows Hb to mix with
the watery medium inside red blood cells.
Outward pointing hydrophilic side chains maintain solubility.
Attached to each polypeptide chain is a prosthetic Haem group with a Fe2+ ion.
Haem group is a prosthetic group (i.e. an important
permanent part of a protein molecule which is not made
from amino acids.)
Haem group has an iron ion (Fe2+) at its centre, and each
Fe2+ ion can combine with one O2 molecule.
The iron combines with oxygen at high oxygen
concentrations and releases oxygen at low oxygen
Human Hb has 4 polypeptide chains with 1 haem group
each and can therefore carry 4 x O2 molecules.
When Hb is bound to O2, it is called oxyhaemoglobin and the colour changes
from purplish red to bright red.
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Collagen is made up of amino-acids, which are
built of carbon, oxygen and hydrogen.
Collagen contains specific amino acids Glycine,
Proline, Hydroxyproline and Arginine.
Collagen is found in bones, skin, tendons,
cartilage, teeth, walls of blood vessels, and
Collagen is a part of the connective tissue that in the skin helps in firmness,
suppleness and constant renewal of skin cells. Collagen is vital for skin