Download The Red Blood Cells

The Red Blood Cells
Introduction
The Red Blood Cells
• The red cells are not true cells in the
strict sense.
• They contain no nucleic acids, and cannot
reproduce.
• They contain no cell organelles and
possess no synthetic activities
Composition of the RBCs
• Red cells contain 35 % solids, mainly Hb
• Hemoglobin, the chief protein of the red cells.
• Other proteins are present in combination with
lipids and oligosaccharide chains, forming the
stroma and cell membrane.
• Potassium, magnesium, and zinc concentrations
in red cells are much higher than in the plasma.
Metabolism
• Erythrocytes contain no mitochondria, so there
is no respiratory chain, no citric acid cycle, and
no oxidation of fatty acids or ketone bodies.
• Energy is obtained from the glycolytic
breakdown of glucose with the production of
lactate.
• ATP produced being used for the Na+ pump.
Metabolism contd.
• Rapoport and Luebering described a special
enzymatic side-pathway in glycolysis.
• Bisphosphoglycerate mutase converts 1,3bisphosphoglycerate(1,3-BPG) to 2,3bisphosphoglycerate(2,3-BPG).
• This reaction wastes the high- energy bond in 1,3BPG without generation of ATP.
• This explain the fact that the red blood cells utilize
more glucose than is required to maintain their
vitality
Metabolism contd.
• The red cells contain an active pentose
phosphate pathway that supplies NADPH
• NADPH is important in keeping glutathione in
the reduced glutathione.
• Reduced glutathione plays a very important
role in the survival of the red blood cells.
• Deficiency of glucose 6- phosphate
dehydrogenase leads to reduced red cell
survival
Metabolism contd.
• The erythrocytes contain carbonic anhydrase.
carbon dioxide combines with water only after it
enters the red cells where hemoglobin, the most
important buffer for the resulting carbonic
acid, is present.
• The red cell also contain rhodanese enzyme
responsible for the detoxication of cyanides.
Red Cell Membrane Structure
• RBCs must be able to squeeze through some tight spots in
microcirculation.
• For that RBCs must be easily & reversibly deformable, its
membrane must be both fluid & flexible .
• About 50% of membrane is protein, 40% is fat & up to 10% is
carbohydrate.
• RBCs membrane comprise a lipid bilayer( which determine the
membrane fluidity), proteins ( which is responsible for flexibility
) are either peripheral or integral penetrating the lipid bilayer.
• Carbohydrates occur only on the external surface.
• The major lipid classes are phospholipids & cholesterol.
Glycoshingolipids as gangliosides including ABO blood group
substances constitute 5-10% of the total lipids.
Red Cell Aging
• Examples of changes occurring in aging red cells:
Increased in old cells
Decreased in old cells
Hb
Glycosylated Hb
Diphosphoglycerate
Membrane
Osmotic fragility
Na+
Binding of IgG
Sialic acid
K+
Lipids and Proteins
G6PD
Pyruvate dehydrogenase
Others
Enzymes
General
Cell density
Sphericity
Deformability
Disc like shape