The Molecular Structure of Haemoglobin

Question 1

Haemoglobin is a ……….. protein which is an ………..

Answer 1

globular

oxygen-carrying pigment

Question 2

What structure does haemoglobin have

Answer 2

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

Question 3

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)

Answer 3

disulphide bonds

hydrophobic inwards

hydrophilic outwards

Question 4

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

Answer 4

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)

Question 5

The prosthetic haem group contains an ………… (Fe2+) which is able to ……….

Answer 5

iron ii ion

to reversibly combine with an oxygen molecule forming oxyhaemoglobin and results in the haemoglobin appearing bright red

Question 6

Each haemoglobin with the four haem groups can therefore carry ………

Answer 6

four oxygen molecules (eight oxygen atoms)