Hemoglobin is the iron-containing protein in red blood cells that transports oxygen throughout the body. It is composed of four polypeptide chains and an iron-containing heme group. Normal hemoglobin levels vary based on age and sex. Hemoglobin transports oxygen from the lungs to tissues and carbon dioxide from tissues back to the lungs. Abnormal hemoglobin variants can lead to conditions like sickle cell anemia and thalassemia. Red blood cells have an average lifespan of 120 days before being broken down, mainly in the spleen.

1. HEAMOGLOBIN
DR HINA MOAZZAM
DEPARTMENT OF PHYSIOLOGY
BUMDC

2. HEMOGLOBIN
• Red pigmented protein /chromoprotein
• Present in RBC`s
• Congugated protein
• Abbreviated Hb or Hgb
• The iron-containing oxygen-transport
metalloprotein in the red blood cells of almost
all vertebrates as well as the tissues of some
invertebrates
• Erythrocyte precursors synthesize Hb; while
the mature erythrocytes lose the property of
synthesizing Hb.

3. NORMAL BLOOD HAEMOGLOBIN LEVELS
• Adult males = 15.5 g/dL (range 14–18 g/dL)
• Adult females = 14 g/dL range 12–15.5 g/dL)
The normal blood Hb concentration at different ages is:
• In fetus, just before birth (from the umbilical cord) ranges from 16.5 to 18.5 g/dL.
• After birth, the Hb concentration increases rapidly and may reach up to 23 g/dL.
➢ the transfusion of cells from the placenta to infant and
➢ haemoconcentration by reduction of plasma volume.
• At the end of 3 months:
• After two days of birth, the Hb levels start falling and stabilize at the end of 3 months to 10.5g/dL.
• At 1 year of age. The concentration then rises gradually to reach 12 g/dL at 1 year of age.

4. HEMOGLOBIN
• The normal Hb becomes 100% saturated when blood is equilibrated with
100% oxygen (PO2, 760 mm Hg)
• One gram of Hb when fully saturated combines with 1.34 mL oxygen.
• Normal values of oxygen carrying capacity:
➢males is 1.34 × 15.5 = about 21 mL%
➢females is 1.34 × 14 = about 18.5 mL%
• Clinically, irrespective of the age, a level of 14.8 g/dL is considered as
100% Hb.

5. STRUCTURE OF HAEMOGLOBIN
• Globular molecule
• Molecular weight of 68,000
• Consists of the protein globin
• Combined with iron
containing pigment called
haem

6. STRUCTURE OF GLOBIN
• Made of four polypeptide chains
• Haemoglobin A (HbA) :
• Two α chains, each containing 141 amino acid
residues
• Two β chains, each containing 146 amino acid
residues.
• Normal adult haemoglobin A is written as HbA
(α2β2)

7. STRUCTURE OF HAEM
• An iron–porphyrin complex called iron–
protoporphyrin IX
• Four pyrrole rings numbered I, II, III and IV,
(tetrapyrroles)
• Joined together by four methine bridges (=CH−).
• The carbon atoms of methine bridges are labelled
α, β, γ and δ.
• Eight side chains are attached to the pyrrole ring at
positions labelled 1–8. These are:
➢Four methyl (H3C) side chains at position 1, 3, 5 and
8.
➢Two vinyl (−CH CH2) side chains at position 2 and 4.
➢Two propionic acid (−CH2 CH2 COOH) side chains
at position 6 and 7.

8. THE IRON
• Iron in the haem is in ferrous (Fe2+) form
• Attached to the nitrogen atom of each
pyrrole ring
• On the iron (Fe2+) a bond is available for
loose union,where:
• In oxyhaemoglobin, O2 is attached
• In carboxyhaemoglobin, CO is attached

9. ATTACHMENT OF HAEM TO GLOBIN
• One molecule of Hb contains four
units of haem
• Each attached to one of the four
polypeptide chains constituting
globin
• Four iron atoms in one molecule of
Hb which can carry four molecules
(eight atoms) of oxygen

10. FUNCTIONS OF HAEMOGLOBIN
1. Transport of O2 from lungs to tissues
• In the lungs, one molecule of O2 is attached loosely and
reversibly at the sixth covalent bond of each iron atom of the Hb
to form oxyhaemoglobin :
Hb + O2→ HbO2
• Oxygenation of first haem molecule in Hb increases affinity of
second haem for oxygen which in turn increases the affinity of
third haem and so on
• The affinity of Hb for fourth oxygen molecule is many times that
for the first molecule
• The affinity of Hb for oxygen is influenced by:
• pH, temperature and concentration of 2,3-DPG (a product of
metabolism of glucose) in the RBCs

13. OXY-HB DISSOCIATION CURVE

14. FUNCTIONS OF HAEMOGLOBIN
2. TRANSPORT OF CO2 FROM THE TISSUES TO THE
LUNGS
• CO2 from the tissues is transported by combining
with amino acids of the globin part
• Deoxygenated Hb forms carbamino-haemoglobin
more readily than oxygenated Hb
• Venous blood becomes more suitable for the
transport of CO2 from the tissues to the lungs.

16. FUNCTIONS OF HAEMOGLOBIN
3. Control pH of the blood :
• The most important acid–base buffer system of blood
• Hb has six times the buffering capacity as compared to the plasma
proteins.

17. VARIETIES OF HAEMOGLOBIN
1. Physiological varieties of Hb
2. Haemolobinopathies

18. PHYSIOLOGICAL VARIETIES OF HAEMOGLOBIN
• Adult haemoglobin or haemoglobin A [HbA (α2β2)]
Two types:
(i) Haemoglobin A [HbA (α2β2)]
• The main form of normal adult Hb
• Its globin part consists of two α and two β polypeptide chains
• It is a spheroidal molecule with a molecular weight of 68,000
(ii) Haemoglobin A2 [HbA2 (α2δ2)]
• Minor component (about 2.5% of the total Hb) in normal adults
• Globin part consists of two α and two δ polypeptide chains.
• δ chains slightly different amino acid composition (out of 146, 10 amino acids are
different) as compared to β chains.

19. PHYSIOLOGICAL VARIETIES OF HAEMOGLOBIN
Fetal haemoglobinor haemoglobin F [HbF (α2γ2)]
• Hb present in the fetal RBCs
• disappears 2–3 months after birth
Structure of HbF:
• Globin part consistsof two α and two γ polypeptide chains (in place of β chains).
• γ chains also have 146 amino acids but its 37 amino acids are different than that of β
chains
Special features of HbF :
• Affinity for oxygen in case of HbF is more than that of HbA
• Resistanceto action of alkalies is more in HbF than HbA
• Life span of HbF is much less (1–2 week) as compared to that of HbA (120 days)

21. HAEMOGLOBINOPATHIES
• Abnormal formation of haemoglobin
• Disorders of globin synthesis; haem synthesis being normal
Two main types:
1. Formation of abnormal polypeptide chains due to substitution of an
abnormal amino acid chain in the HbA. Eg ,Haemoglobin S.
2. Suppression of synthesis of polypeptide chain of globin eg.
Thalassaemia.

22. SICKLE CELL ANEMIA
Sickle cell haemoglobin.(HbS)
• Substitution of Valine for Glutamic Acid at 6th position in beta chain.
• When HbS is reduced (in low O2 tension) precipitate into crystals in RBC, changes
shape & become Sickle shaped.
• Less flexible – blockage of microcirculation.
• Increases blood viscosity.
• More fragile – More Hemolysis – Anaemia.

23. THALASSEMIA
• Thalassemia is an inherited blood
disorder in which the body makes an
abnormal form of hemoglobin
• Abnormality or mutation in one of the
genes involved in hemoglobin
production.
• The disorder results in excessive
destruction of red blood cells, which
leads to anemia.
• In beta thalassemia, the beta globin
genes are affected

25. DERIVATIVES OF HAEMOGLOBIN
• Haemoglobin readily react with any gas, other substance
1. Oxyhaemoglobin.
• An unstable and reversible compound
• Iron remains in the ferrous state.
2. Reduced haemoglobin or deoxygenated haemoglobin
• oxygen is released from the oxyhaemoglobin.
• HbO2 → Hb + O2
• (Oxyhaemoglobin) → (Reduced haemoglobin)
3.Carbamino-haemoglobin :withcarbon dioxide
HbNH2 + CO2 → HbNHCOOH

26. DERIVATIVES OF HAEMOGLOBIN
4. Carboxyhaemoglobinor carbon monoxyhaemoglobin ,Hb with carbon monoxide (CO)
Hb + CO → COHb
• The affinity of Hb for CO is much more (200–250 times) than its affinity for oxygen
• CO poisoning
5. Methaemoglobin.When reduced or oxygenated Hb is treated with an oxidizing
agent, e.g. potassium ferricyanide, the ferrous Fe2+ is oxidized to ferric (Fe3+); the sixth
bond is attached to OH to form the compound methaemoglobin. Methaemoglobin is
represented as HbOH.It cannot unite reversibly with gaseous oxygen; the O2 of the
attached OH is not given off in a vacuum
6. Glycosylated haemoglobin
• A1C (HbA1C), glucose is attached to terminal valine in the β chains
• Diabetes mellitus

28. SYNTHESIS OF HAEMOGLOBIN
SYNTHESIS OF HAEM
• Haem is synthesized in the mitochondria.
• Succinyl-CoA (derived from the citric acid cycle in
mitochondria) and glycine are the starting
substancesin the synthesis of haem.
• These condense to form α-amino-β-ketoadipic acid.
• The condensation requires pyridoxal phosphate for
activation of glycine.
• The protoporphyrin IX is then formed after a series
of reactions promoted by other enzymes.
• Finally, ferrous ion is introduced into the
protoporphyrin IX molecule to form haem in a
reaction catalyzed by the enzyme haem synthetase.
.

29. SYNTHESIS OF GLOBIN
Globin, the protein part of the Hb, is
synthesized in the ribosomes

30. FACTORS CONTROLLING HAEMOGLOBIN FORMATION
1. Role of proteins
• provide amino acids required for the synthesis of globin part of the Hb.
• A low protein intake retards Hb regeneration even in the presence of excess iron; the
limiting factor being lack of globin
2. Role of iron:necessary for formation of the haem part of haemoglobin
• In addition to dietary iron, the iron released by degradation of RBCs is also reused for
the synthesis of Hb
3. Role of other metals :
• Copper is essential for the Hb synthesis, as it promotes the absorption, mobilization
and utilization of iron
• Cobalt increases the production of erythropoietin which in turn stimulatesRBC
formation
• Calcium reported to help indirectly by conserving iron and its subsequentutilization

31. FACTORS CONTROLLING HAEMOGLOBIN FORMATION
4. Role of vitamins:
• Vitamin B12, folic acid, and vitamin C
• Help in synthesis of nucleic acid which in turn is required for the
development of RBCs.
• Also helps in absorption of iron from the gut
5. Role of bile salts.
• Necessary for proper absorption of metals like copper and nickel which
in turn are essential factors for synthesis of Hb

32. LIFE SPAN OF RBCs
THE AVERAGE LIFE SPAN OF RBCS IS 120 DAYS
Causes of reduction in the life span of RBCs:
I. Defects in RBCs (Corpusculardefects)
• Hereditary spherocytosis,
• Sickle cell anaemia,
• Thalassaemias,
• Deficiency of red cell enzymes,
• Glucose 6-phosphate-dehydrogenasedeficiency
• Pyruvate kinase deficiency
II. Extracorpuscular defects
• Transfusion of mismatched blood,
• Autoimmune haemolytic disorders and Hypersplenism.

33. FATE OF RBCS
• The cell membrane of old RBCs (after about 120 days) becomes more
fragile due to decreased NADPH activity
• The destruction of red cells occurs mostly in the capillaries of spleen
because they have very thin lumen
• Spleen is also called the graveyard of RBCs
• The haemoglobin released after the haemolysis of red cells is taken
up by the tissue macrophages.

34. FATE OF RBCS
The tissue macrophage system (reticuloendothelial system) ,Includes the
following phagocytic cells:
• In the bone marrow these cells form part of the lining of the blood
sinuses (littoral cells),
• In the liver they lie at intervals along the vascular capillaries(Kupffer
cells),
• In the spleen they are found in the pulp
• In the lymph nodes they line the lymphatic paths

35. FATE OF HAEMOGLOBIN
• In the macrophages, the haem part of the haemoglobin molecule is altered by
oxidation of one of its methine (=CH) bridges.
• The tetrapyrrole ring structure is broken and four pyrrole groups become arranged
as a straight chain
• The green iron-containing compound choleglobin is formed
• choleglobin splits off into globin, iron and biliverdin (tetrapyrrole straight chain free
from globin and iron).
• Globin is degraded into amino acids and joins the amino acid pool of plasma and is
released.
• Iron released into the circulation is:
• – carried into the bone marrow for reutilization
• – in the other tissues it combines with apoferritin to form the ferritin (storage form
of iron).
• Biliverdin (tetrapyrrole straight chain free from globin and iron) is converted into
bilirubin (by the enzyme biliverdin reductase) and is released into the blood.

36. FATE OF HEMOGLOBIN