1. Biochemistry of blood.
Respiratory function of
erythrocytes.
Pathobiochemistry of blood.

3. Blood performs three major
functions:
 transport through the body of
 oxygen and carbon dioxide
 food molecules (glucose, lipids, amino acids)
 ions (e.g., Na+, Ca2+, HCO3−)
 wastes (e.g., urea)
 hormones
 defense of the body against infections and other foreign
materials. All the WBCs participate in these defenses.
 Homeostatic functions
- heat
- water- salt balance
- Acid – base balance

5. Red Blood Cells (erythrocytes)
The most numerous type in the blood .
•Features:
•The erythrocytes doesn’t contain nucleus, chromatine
•The erythrocytes doesn’t contain mytochondrias, thus АТP
producing due to the anaerobic glycolisis till to the lactate
(∼90%).
•The glycolisis has features. During it the 2,3 BPG will be
produced, not 1,3 BPG. This compound need for joining О2 to
hemoglobin: low concentration of 2,3 BPG will increase the
affinity hemoglobin (Нв) to О2.
• The PPP is the main path for producing of reductive
equivalents NADPН2 for taking part in glycolisis

6. Red blood cells are responsible for the
transport of oxygen and carbon dioxide.
 In adult humans the
hemoglobin (Hb) molecule
consists of four
polypeptides:
 two alpha (α) chains of
141 amino acids and
 two beta (β) chains of
146 amino acids
 Each of these is attached
the prosthetic group heme.
 There is one atom of iron at
the center of each heme.
 One molecule of oxygen
can bind to each heme.
 The reaction is reversible.

12.  The iron atom may either
be in the Fe2+ or Fe3+
state, but ferrihemoglobin
(methemoglobin) (Fe3+)
cannot bind oxygen. In
binding, oxygen
temporarily oxidizes Fe to
(Fe3+), so iron must exist
in the +2 oxidation state in
order to bind oxygen. The
body reactivates
hemoglobin found in the
inactive (Fe3+) state by
reducing the iron center.

17. Carbon Dioxide Transport
 Carbon dioxide (CO2) combines with water forming
carbonic acid, which dissociates into a hydrogen ion
(H+) and a bicarbonate ions:
 CO2 + H2O ↔ H2CO3 ↔ H+ + HCO3−
 95% of the CO2 generated in the tissues is carried in
the red blood cells:
 It probably enters (and leaves) the cell by diffusing
through transmembrane channels in the plasma
membrane. (One of the proteins that forms the
channel is the D antigen that is the most important
factor in the Rh system of blood groups.)
 Once inside, about one-half of the CO2 is directly
bound to hemoglobin (at a site different from the one
that binds oxygen).

18.  The rest is converted — following the equation above —
by the enzyme carbonic anhydrase into
 bicarbonate ions that diffuse back out into the plasma
and
 hydrogen ions (H+) that bind to the protein portion of
the hemoglobin (thus having no effect on pH).
 Only about 5% of the CO2 generated in the tissues
dissolves directly in the plasma.
 When the red cells reach the lungs, these reactions are
reversed and CO2 is released to the air of the alveoli.

19. Hb Equilibrium
 H+, CO2,
ab BPG

α β
b a O2 β α
R T
(low affinity)
(high affinity)

20. The ability of hemoglobin to release oxygen, is affected by pH, CO2
and by the differences in the oxygen-rich environment of the lungs and
the oxygen-poor environment of the tissues. The pH in the tissues is
considerably lower (more acidic) than in the lungs. Protons are
generated from the reaction between carbon dioxide and water to form
bicarbonate:
 CO2 + H20 -----------------> HCO3- + H+
This increased acidity serves a two fold purpose.
- First, protons are lower the affinity of hemoglobin for oxygen,
allowing easier release into the tissues. As all four oxygens
are released, hemoglobin binds to two protons. This helps to
maintain equilibrium towards the right side of the equation.
This is known as the Bohr effect, and is vital in the removal of
carbon dioxide as waste because CO2 is insoluble in the
bloodstream. The bicarbonate ion is much more soluble, and
can thereby be transported back to the lungs after being
bound to hemoglobin.
- If hemoglobin couldn’t absorb the excess protons, the
equilibrium would shift to the left, and carbon dioxide couldn’t
be removed

21.  In the lungs, this effect works in the reverse
direction. In the presence of the high oxygen
concentration in the lungs, lead to the proton
affinity decreasing. As protons are shed, the
reaction is driven to the left, and CO2 forms as
an insoluble gas to be expelled from the lungs.
The proton poor hemoglobin now has a greater
affinity for oxygen, and the cycle continues.

22. Bohr Effect (pH)
100 mm O2
20 mm O2

23. CO2 effect
20 mm CO2
80 mm CO2

24. Effect of BPG
BPGEffect BPG is the main
Hb alone player in Hb
100
cooperativity.
80
60
Hb + BPG High altitude
40 increases BPG,
20
pushing curve
0
pO2 vs p50=8
pO2 vs p50=26 further to right
0 20 40 60 80 100 120 140 160
pO2 (mm Hg)

25. Cooperativity
 Oxygen binding to one subunit of Hb,
increases the affinity of the other subunits
for additional oxygens. In other words, the
first one is the hardest, the rest are easy.
 Anaemia
 Anaemia is a shortage of RBCs and/or the
amount of haemoglobin in them.

26. Myoglobin and Hemoglobin
 Mb is monomer, Hb is a tetramer (ex. a2b2).
 Hb subunits are structurally similar to Mb, with 8
a-helical regions, no b-strands and no interior
water.
 Both contain one heme prosthetic group per
chain.
 Both Mb and Hb contain proximal and distal
histidines.
 Affinity of Mb for oxygen is high, affinity of Hb for
oxygen is lower and more variable.

28. Sickle cell hemoglobin (HbS)
-
G lu
G lu
-
αβ αβ
αβ
βα βα
-
βα
G lu H bS H bS
H bA (h e te ro z y g o u s ) (h o m o zy g o u s)
1
S ic k le c e ll tra it S ic k le c e ll d is e a s e

29. Polymerization of HbS
αβ αβ
αβ
α β βαβα
αβ βα
αβ βα Association shown in
αβ βα previous figure is
βα repeated over and over
to produce large, rod-like
βα aggregates that bind
oxygen poorly and distort
shape of erythrocytes.

30.  Sickle cell trait is usually asymptomatic, but
strenuous exercise at altitude could elicit
sickling and destruction of erythrocytes.
This lowers serum Hb and hematocrit, while
raising Hb breakdown products such as
bilirubin, which can accumulate to form
gallstones.

31. α Thalassemias
 Rare, since α gene is duplicated (four genes per diploid
chromosome set).
 Usually more severe than β thalassemia because
 there is no substitute for α gene in adults.
 Almost all α thalassemias are deletions
 In α thalassemia intermedia (αoα/αοαo) -
appearance of HbH (β4)
 In α thalassemia major (αoαο/αoαo), Hb Bart’s
(γ4) is predominant (usually lethal).
 BPG is ineffective in HbH & Hb Bart’s.

32. β Thalassemias
 More common, since β gene is present in only
one copy per chromosome.
 Less severe than α thalassemia, since δ chain
can effectively substitute in adults.
 The γ chain can also persist into adulthood
(HPFH).
 In βδ thalassemia major (βδ0/βδ0) excess α
chains do not form soluble homotetramers.