Structure and function of hemoglobin

Hemoglubin is are carrier protein for oxygen and CO2. it a pigmented and globular protein present within the red blood cell, its structure, synthesis, and how it function in the transportation of oxygen and CO2 are given in this presentation

1. Structure and function of
Haemoglobin
Muhammad Asif Zeb
Lecturer Hematology
IPMS-(KMU)

3. Introduction
Haemoglobin (Hb), protein constituting 1/3 of
the red blood cells

65% at erythroblast stage
35% at reticulocyte stage
normal concentration of Hb in the blood:
adult males 13.5 – 16.5 g/dL
adult females 12.5 – 15 g/dl


Two parts
Haem
Globin

4. Synthesis of Haemoglobin (Hb)
Haem & globin produced at two different
sites in the cells

Haem in mitochondria
Globin in ribosomes

Well synchronized

5. Synthesis of Haemoglobin

6. Structure of Haem

7. Synthesis of globin

8. Synthesis of globin
Various types of globin combines with
haem to from different haemoglobin

Eight functional globin chains, arranged in
two clusters the
b- cluster (b, g, d and e globin genes) on the short
arm of chromosome 11
a- cluster (a and z globin genes) on the short arm
of chromosome 16

10. Globin gene clusters

11. Globin synthesis, starts at 3
rd
week of
gestation
Embryonic
Haemoglobin Gower I ( z
2e
2)
Haemoglobin Portland ( z
2g
2)
Haemoglobin Gower II (a
2e2)
Fetal : HbF (a
2g
2), HbA (a
2b
2)
Adult : HbA, HbA2 ( a
2d
2), HbF.
Synthesis of globin

12. Globin chain switch

13. Hb A Hb A
2 Hb F
structure a
2b
2 a
2d
2 a
2g
2
Normal % 96-98 % 1.5-3.2 % 0.5-0.8 %
Adult haemoblobin

14. Function of Hb

16. Functions of Haemoglobin
Oxygen delivery to the tissues
Reaction of Hb & oxygen

Oxygenation not oxidation
One Hb can bind to four O2 molecules
Less than .01 sec required for oxygenation
b chain move closer when oxygenated
When oxygenated 2,3-DPG is pushed out
b chains are pulled apart when O2 is unloaded,
permitting entry of 2,3-DPG resulting in lower
affinity of O2

17. Oxy & deoxyhaemoglobin

18. Oxygen-haemoglobin dissociation
curve
O2 carrying capacity of Hb at different Po2

Sigmoid shape
Binding of one molecule facilitate the second
molecule binding

P 50 (partial pressure of O2 at which Hb is half
saturated with O2) 26.6mmHg

19. Hb-oxygen dissociation curve

20. The normal position of curve depends on

Concentration of 2,3-DPG
H
+
ion concentration (pH)
CO
2 in red blood cells
Structure of Hb
Hb-oxygen dissociation curve

21. Right shift (easy oxygen delivery)

High 2,3-DPG
High H
+
High CO
2
HbS

Left shift (give up oxygen less readily)
Low 2,3-DPG
HbF
Hb-oxygen dissociation curve

22. Derivatives of hemoglobin
 Oxyhemoglobin (oxyHb) = Hb with O
2

 Deoxyhemoglobin (deoxyHb) = Hb without O
2

 Methemoglobin (metHb) contains Fe
3+
instead of Fe
2+
in heme groups

 Carbonylhemoglobin (HbCO) – CO binds to Fe
2+
in heme in case of CO
poisoning or smoking. CO has 200x higher affinity to Fe
2+
than O
2.

 Carbaminohemoglobin (HbCO
2) - CO
2 is non-covalently bound to globin
chain of Hb. HbCO
2 transports CO
2 in blood (about 23%).

 Glycohemoglobin (HbA1c) is formed spontaneously by nonenzymatic
reaction with Glc. People with DM have more HbA1c than normal (› 7%).
Measurement of blood HbA1c is useful to get info about long-term
control of glycemia.

23. Summary
Normal structure including the proportion of
globin chains are necessary for the normal
function of haemoglobin

Reduced haemoglobin in the red blood cells due
to any abnormality of any of its constituents
result into a clinical situation called anaemia

Metabolic & other abnormalities result into
abnormal oxygen supply to the tissue