Haemoglobin Flashcards
why do we need haemoglobin?
Respiration is the process in which organisms convert nutrients into useful energy in the presence of O2.
In this, O2 must be carried from lungs to tissues
Cells must have an efficient O2 carrying molecule - this is haemoglobin
As well as O2 transport it also transports CO2 and protects against pH change
describe the structure of haemoglobin
A haemoglobin molecule is composed of four protein globin chains, each centred around a haem group.
In most adult haemoglobin, there are two alpha chains and two beta chains.
where does haem, globin, and haemoglobin synthesis mostly take place?
Haem synthesis occurs mainly in mitochondria
Globin synthesis occurs mainly in the polyribosomes
65% haemoglobin is synthesised in the erythroblasts, 35% in the reticulocytes
what is the difference between embryonic and foetal, and adult Hb?
Embryonic and Foetal haemoglobin have a higher affinity for O2
Haem is composed of a _______ ring with Fe2+ in the middle.
Iron is brought to the developing red cells by a carrier protein called _______ which attaches to special binding sites on the surface of these cells.
Transferrin releases ___ and returns back to circulation.
Haem is synthesised from the combining of porphyrin and Fe2+ in the _________
Haem is composed of a PORPHYRIN ring with Fe2+ in the middle.
Iron is brought to the developing red cells by a carrier protein called TRANSFERRIN which attaches to special binding sites on the surface of these cells.
Transferrin releases IRON and returns back to circulation.
Haem is synthesised from the combining of porphyrin and Fe2+ in the MITOCHONDRIA
Lead can bind two key enzymes in the haem synthesis pathway- what are they?
- Porphobilinogen synthase
* Ferrocheletase
As well as causing microcytic anaemia, what is the action of lead on haem sythesis thought to do?
to contribute to the toxic effect on the brain as high ALA is thought to lead to some of the neurological effects of lead poisoning.
what is haem and what does it do in haemoglobin?
The active site is a non-protein group called haem (heme). A haem group sits in the pocket of each hydrophobic globin protein.
It is haem which gives the blood its characteristic red colour. Oxygenated haemoglobin is bright red but deoxygenated haemoglobin is darker red.
Structure of both Haem and Globin are able to be _______.
To hold it in place Fe2+ binds to _ nitrogen atoms in the _______ ring
Fe2+ also needs to bind to O2 and to globin which it does by 2 other binding sites on either side of the ring, one binds to _____ and one binds to a ________ residue on globin Fe2+
Structure of both Haem and Globin are able to be MODIFIED
To hold it in place Fe2+ binds to 4 nitrogen atoms in the PORPHYRIN ring
Fe2+ also needs to bind to O2 and to globin which it does by 2 other binding sites on either side of the ring, one binds to OXYGEN and one binds to a HISTIDINE residue on globin Fe2+
What happens to iron when haemoglobin is oxygenated
Fe2+ moves into the plane of porphyrin ring.
what does oxygenation of 1 haem group do?
changes the shape of the tertiary globin structure
As the four globin molecules of Hb are associated changes to the shape of one globin molecule affects the others in this case so they are more likely to bind O2.
how does Hb’s affinity for oxygen increase?
Oxygen binds to one haemoglobin molecule
This increases the affinity of the 3 remaining molecules to bind O2.
This further increases the the affinity of the remaining 2 molecules to bind O2 which further increases the affinity of the remaining molecule to bind O2
what is cooperativity
Haemoglobin is fully saturated with O2
Oxyhaemoglobin circulates to deoxygenated tissues -what happens?
Here O2 is unloaded and the affinity of Haemoglobin for O2 is decreased
what happens where O2 tensions are very low, e.g. active tissues
the affinity of haemoglobin for O2 is low and maximal delivery of O2 is achieved
