L1, Metabolism of red blood


 L1, Metabolism of red blood

Introduction: Red blood cells (RBCs) have highly specialized function: to deliver the maximum quantity of oxygen to tissues and in the removal of carbon dioxide. Therefore, the structure and composition of Red blood cells reflect these functions. I - The blood's red color is due to iron in hemoglobin. 2- Mature RBCs are devoid of nuclei and all other cellular organelles. This provides more space for carrying hemoglobin. 3- RBCs has a biconcave

Importance of RBCs bi-concave shape: l. This shape possesses a much higher surface area. It allows considerable alteration of the cell volume without increasing the tension of the cell wall. 2. It can easily squeeze when it pass through capillary 3. Hemoglobin remains distributed in a very thin layer. This facilitates quick saturation or desaturation with the gases.

Red blood cells cytoskeleton: • The red blood cell membrane is a lipid bilayer. • The membrane is linked to the cytoskeleton Of the RBC which consists of long strands Of alpha and and actin filaments • Spicrtin forms the inner shell Of the RBC and gives the cell its deformability. • Spectrin is bound to the membrane at sites containing the anion exchanger (band dna nirykna ,snietorp lateleksotyc aiv )3 .nicudda • Defects in this protein (spectrin). results in abnormal RBCsand the condition Of hereditary spherositosis in human

Hexomomophosphste shunt (HMB shunt( Definition: It is an alternative minor pathway for glucose oxidation involving the formation of pentoses as intermediates. Site: Cytosol of some cells: - RBCs. - Liver, adipose tissue & lactating mammary gland (F.A synthesis). - Adrenal cortex, gonads & placenta (steroid synthesis). - Retina, cornea, lens (source of energy & reduction of retinal to retinol).

Functions of HMP shunt: l- Production of NADPH+H+ which is used in the: - Synthesis of fatty acids. - Synthesis of cholesterol. - Synthesis of certain steroid hormones. 2- Production of pentoses 5 —P (ribulose, xylulose & ribose 5-P) which is important in: a. Formation of (base —pentose) b. Formation Of nucleotides (base —pentose-p)c. Formation of nucleic acids and nucleo-protein.

Hexose Monophosphate Shunt HMP can account for complete oxidation of glucose where it is converted to 6 molecules of C02 and12 molecules of NADPH +H as follows: 6 Glucose -6-P + 12 NADP➡️ 6 Ribulose-5-P + 6 C02 + 12 NADPH+H

Hexose Monophosphate Shunt

In tissues (muscles) where oxidative HMP is

not active due to deficiency of the dehydrogenases of the oxidative phase

and incases of favism (deficiency ofG6PD).

Are formed byreversal of the non oxidative phase.