Hemoglobin is a protein molecule in red blood cells that carries oxygen from the lungs to the body's tissues and returns carbon dioxide from the tissues back to the lungs. It is made up of four heme groups, each bound to a globin protein chain. Hemoglobin plays a crucial role in maintaining the body's oxygen balance and is essential for overall health. Variations in hemoglobin levels can indicate different health conditions, such as anemia or dehydration.

1. Hemoglobin
Structure and Function

2. Haemoglobin:
•Haemoglobin is a type of globular protein present
in red blood cells (RBCs), which transports
oxygen in our body through blood. It is a
tetrameric protein and contains the heme
prosthetic group attached to each subunit.
•It is a respiratory pigment and helps in
transporting oxygen as oxyhaemoglobin from the
lungs to different parts of the body. Some amount
of carbon dioxide is also transported back via
haemoglobin as carbaminohaemoglobin.

3. Haemoglobin:
•The haemoglobin level is measured in g/dL of
the blood. In a healthy individual, the level
ranges from 12 to 20 g/dL. Generally Hb level
in males is greater compared to females.
•The normal level in Males is 13.5 to 17.5 g/dL
and in Females, it is 12 to 15.5 g/dL.

4. Haemoglobin Structure:
Max Perutz described the molecular structure of haemoglobin
in 1959. Haemoglobin is a tetrameric protein. The main type
of haemoglobin in adults is made up of two subunits each of ‘
𝜶’ and ‘𝝱’ polypeptide chains. Each polypeptide chain is
linked to a heme prosthetic group.
•𝜶 subunit – It is made up of alpha polypeptide chain having
141 amino acid residues.
•𝝱 subunit – It is made up of beta polypeptide chain having
146 amino acid residues.
•Heme group – It is an iron-containing prosthetic group,
which is attached to each polypeptide chain. It contains iron in
the centre of the porphyrin ring.

5. Haemoglobin Structure:
• Hemoglobin is a protein ( Heme+protein )
• Types of proteins are
 globular proteins ( functional proteins )
 linear proteins ( structural proteins )
 There are four iron atoms in each molecule of
hemoglobin, which, accordingly, can bind four atoms
of oxygen.
• Hb is considered of globular proteins.
• Mature RBCs do NOT synthesis Hb, while immature
RBCs synthesis Hb.
• Mitochondria is very important for Heme synthesis

6. Hemoglobin = Heme + globin ( protein )
Note : globin is considered as a protein so
that it synthesized by RER.

7. Structure of heme

8. Each hemoglobin molecule ( Globular protein ) consists of
1. 4 Heme
2. 4 linear proteins each one bind to a Heme

9. Heme synthesis
• Heme = Protoporphyrin + Iron
• Protoporphyrin = Iron free Heme
• Protoporphyrin consist of 4 pyrrol rings.
• Iron have 6 coordination, 4 bind with these 4
pyrrol rings of protoporphyrin, 1 bind with
histidine ( amino acid ) from globulin and 1
is free (bind to Oxygen , CO2 respectively)

11. Iron in Hemoglobin is ferrous or ferric ? Why ?
• Iron in ferrous form ( 6 coordination )
1) 4 bind with protoporphyrin
2) 1 bind to histidine ( globin )
3) 1 free bind to O2 or CO2 respectively
• Where in ferric form we well have one bond
missing ( malfunctional hemoglobin )
• Heme and globulin are not isolated, they bind
together by Iron,

12. Types of Hemoglobin Normal
• Different types of Hb due to different type
of globin NOT Heme.
and small amount of
• Adult have HbA
HbA2.
• Fetus Have HbF.

13. Types of Hemoglobin
Type Formula
HbA (95-98%) α2β2
HbA2 (2-3%) α2δ2
HbF (upto 2.5%) α2γ2
 HbF have more affinity to oxygen than HbA.

14. Gas Transportation
• Why we use hemoglobin as a transporter for
oxygen ?
1. Because of low solubility of oxygen in
water.
2. Hemoglobin have a regulatory effect on
oxygen concentration in lungs and tissues.
Note : all tissue required of oxygen and 20% of
CO2 from metabolic wastes transport via Hb.

15. Allosteric effect
• When an enzyme reacts to effectors with
conformational changes that increase or
reduce its activity, it is said to show
allosteric behavior
• Many substances act on Hb as an allosteric
substances.
• Although Hb is NOT an enzyme, but it have
all the characteristics of enzymes

16. • Substances that have an allosteric effect
on Hb are :
1. 2,3 DPG (Intermediate factor in glycolysis)
2. H+ ( i.e. ph effect on Hb )
3. CO2

17. Forms of Hb
• When Hb have high affinity to oxygen in
lung is called ( oxyhemoglobin ) and
refereed to as R form ( R from Relax )

18. • When Hb have low affinity to oxygen in
tissue is called ( deoxyhemoglobin ) and
refereed to as T form ( T from Tense )

19. Steps for O2- CO2 Transport
1. In lungs, Pressure of oxygen is high so it
diffuse from outside the body to inside the
body and bind with Hb. (bond of one O2 to
hemoglobin facilitate the binding of other O2
molecule).
2. In tissues, hemoglobin bind to 2,3 DPG and
that cause to decrease affinity of Hb to Oxygen
and releasing Oxygen to the tissues.