Blood(Biochemistry)

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BLOOD
Connective Tissue
Cells (45%) suspended in fluids (Plasma- 55%)
Delivers necessary substances such as nutrients and oxygen to body’s cells and transport waste products away from those cells
•      Plasma
•      Red Blood cells
•      Platelets
•      White Blood Cells
•      Metabolism in Reticulocytes
Reticulocytes—immature red blood cells
–    Develops and matures in red bone marrow
–    Anucleated
–    Enters circulation, loses intracellular organelles (eg, mitochondria, ER etc) and ribosome within 24 hrs    Becomes young RBC & loses ability to
synthesize proteins      
–    Contains cytoplasmic organelles
–    Synthesize proteins and lipids
–    Energy required was provided by two strategies– oxidative phosphorylation and aerobic glycolysis
Metabolism in Red Blood Cells
Non-nucleated
No intracellular organelles (eg, mitochondria, golgi apparatus, lysosomes etc)
Simple function of delivering O2 to tissues and disposal of CO2 and proton formed by tissue metabolism
HOWEVER , they are NOT METABOLICALLY INERT– produces ATP required to maintain biconcave shape & transport of ions and water
Metabolism in Red Blood Cells
Highly glucose dependent for energy, so membrane has high affinity glucose transporters
Glycolysis produces ATP
No mitochondria, hence no oxidative phosphorylation
Produces 2,3-BPG which regulates the ability of Hb to transport oxygen
PPP is operative in RBC (5-10% of total glucose flux), produces NADPH which involves Glucose-6-Phosphate Dehydrogenase , deficiency leads to Hemolytic Anemia
Metabolism in Red Blood Cells
RBC counteracts toxic peroxides through reduced Glutathione (GSH)
RBC requires NADPH to return oxidized glutathione (GSSG) to the reduced state (GSH).
The iron of Hb is maintained in ferrous state. Ferric iron is reduced to ferrous state by the action of NADH-dependent methemoglobin reductase
Metabolism in Red Blood Cells
Synthesis of glycogen, fatty acids, protein and nucleic acids does not occur in RBC.
After RBC is destroyed, the globin is degraded to amino acids (reutilized by body), iron released from heme and reutilized, the tetrapyrrole component of heme is converted to bilirubin and excreted into the bowel via bile.
•      Metabolism in Leukocytes
High rate of aerobic and anaerobic glycolysis
Active Pentose Phosphate Pathway
Moderate oxidative phosphorylation
Rich in lysosomes and degradative enzymes
Contains certain unique enzymes (eg, myeloperoxidase and NADPH-oxidase) and proteins (eg, cluster of differentiation- CD proteins)
•      Metabolism in Platelets
Platelets:- granular, non-nucleated fragments of cytoplasm
Contains organelles
Involved in hemostasis
Natural source of growth                                factors (eg PDGF, IGF-1)
Anaerobic glycolysis considerably more intense than aerobic
Metabolism in Platelets
Coagulation and Hemostasis
Coagulation
–    a complex process , blood forms clot.
–    Important part of hemostasis
–    Intrinsic and Extrinsic Pathway
–    Various factors, cofactors, proteins and ions are involved
•      Hemostasis
–     Cessation of blood loss from damaged vessel
–    Activated platelets and fibrin is involved
•      Factors Involved in hemostasis
•      Functions of protein involved in blood coagulation
•      Functions of protein involved in blood coagulation
•      Anticoagulants
•      Substance that prevents coagulation
•      Anticoagulants used in laboratory:
–    EDTA  (EthyleneDiamineTetraAcetic acid)
–    Oxalate
–    Fluoride
–    Citrate
•      Chelates/ binds calcium in the blood
•      Sequesters metal ions
•      Metal ions remain in the solution but exhibit diminished reactivity

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