The Molecular Structure of Haemoglobin
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Haemoglobin is a ……….. protein which is an ………..
globular oxygen-carrying pigment
What structure does haemoglobin have
it has a quaternary structure as there are four polypeptide chains These chains or subunits are globin proteins (two α–globins and two β–globins) and each subunit has a prosthetic(permanent non protein part of a protein) haem group
The four globin subunits are held together ………….. and arranged so that their ………… R groups are facing ……….. (helping preserve the three-dimensional spherical shape) and the hydrophilic R groups are facing …………. (helping maintain its solubility)
disulphide bonds hydrophobic inwards hydrophilic outwards
The arrangements of the R groups is important to the functioning of haemoglobin. If changes occur to the sequence of amino acids in the subunits this can result in the
this can result in the properties of haemoglobin changing. This is what happens to cause sickle cell anaemia (where base substitution results in the amino acid valine (non-polar) replacing glutamic acid (polar) making haemoglobin less soluble)
The prosthetic haem group contains an ………… (Fe2+) which is able to ……….
iron ii ion to reversibly combine with an oxygen molecule forming oxyhaemoglobin and results in the haemoglobin appearing bright red
Each haemoglobin with the four haem groups can therefore carry ………
four oxygen molecules (eight oxygen atoms)