Molecules, Genes and Disease

Question 1

Describe the structure of haemoglobin

Answer 1

Globular protein with quaternary structures. Made up of 4 units - a tetramers, 2 alpha and 2 beta chains. Each chain as a haem group with an iron atom, which can each bing one O2 molecule.

Question 2

Describe the affinity states of haemoglobin. What is the advantage of this? what is this known as?

Answer 2

When one O2 molecule binds it changes from the T state to the R state, making it easier for subsequent molecules to bind. It is therefore more sensitive to small changes in O2 level. This is known as cooperative binding.

Question 3

What are allosteric effectors of haemoglobin? What is the Bohr effect?

Answer 3

molecules which influence the behaviour of proteins. BPG reduces O2 affinity and promotes deposition of O2 in tissues. H+ and CO2, metabolic products have the same effect ,causing oxygen deposition in more metabolically active tissue. This is known as the Bohr effect.

Question 4

What happens in sickle cell anaemia?

Answer 4

A to T point mutation results in Glu to Val substitution in Beta chain. Results in polymerisation of the haemoglobin when in a tense state, producing ‘sickle cells’ RBCs. These RBCs are inflexible and can block small vessels.

Question 5

What is different about fetal haemoglobin?

Answer 5

made up of alpha and theta chains which have a higher affinity than the maternal haemoglobin.

Question 6

What is thalassemia?

Answer 6

Inherited blood disorder. Decrease or absence of either the alpha or beta haemoglobin sub units. Lack of alpha subunits will present prenatally. Beta thalassemia wont present until after birth because fetal haemoglobin does not contain the beta sub unit.