Structure of Haemoglobin
description
Transcript of Structure of Haemoglobin
STRUCTURE OF HAEMOGLOBIN
1 RBC consists of approximately 250 million Hb molecules
STRUCTURE OF HB- GENERAL
Haemoglobin is a hemoprotein only found in the cytoplasm of RBC transports O2 and CO2 between lungs and various tissues normal concentration of Hb in the blood: adult males 135 – 175 g/L adult females 120 – 168 g/L
STRUCTURE
Made up of heme + Globin
4 polypeptide Subunits
Heme group Porphyrin ring Ferrous iron
Globin chain 2 Alpha Chains 2 Beta chains
HEME STRUCTUREHEME IS A METALOPORPHYRINE(CYCLIC TETRAPYRROLE)
Heme contains: conjugated system of
double bonds → red colour
4 nitrogen (N) atoms
1 iron cation (Fe2+)→ bound in the middle of tetrapyrrole skeletal by coordination covalent bonds
methine bridge pyrrole ring
PROPERTIES OF IRON IN HEME
• Coordination number of iron in heme = 6
6 bonds:• 4x pyrrole ring
(A,B,C,D)• 1x link to a protein• 1x link to an oxygen
STRUCURE OF GLOBINGlobin: Four polypeptide chains in one
molecule of Hb Adult Hb(Hb A) has four
polypeptide chains 2 α variety & 2 β variety α consists of 141 AA and β 146
AA HbA is symbolised α2 β2 Other types of normal Hb: o Hb F (α2ɣ2) o Hb A2(α2δ2) (2.5% of HbA)
STRUCURE OF HAEMOGLOBIN
• With each of 4 polypeptide chains one haem molecule is attached
• Each haem part contains one iron molecule• With each iron molecule, one molecule O2 can
combine• With each molecule of Hb, 4 molecules of O2
can combine• Structure changes slightly during binding &
release of O2
BOND OF HAEMOGLOBIN
Bonds between α1 & β2 chains are weaker than α1, β1.
α1 & β2 are able to move and get twisted, allowing change between tense and relaxed form.
Tense form is present in deoxygenated Hb Β chains move away from each other 2,3
DPG binds here. Presence of 2 3 DPG increases O2
delivery to tissues Relaxed form is present in Oxygenated
Hb. 2 3 DPG expelled allowing further O2
binding.
Quaternary structure of deoxy- and oxyhemoglobin
T-state (deoxy-state) R-state (oxy-state)
THANK YOU