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Blood: Cells and Plasma Proteins Beth A. Bouchard BIOC 212: Biochemistry of Human Disease

Blood: Cells and Plasma Proteins Beth A. Bouchard BIOC 212: Biochemistry of Human Disease Spring 2005. I. Major functions of blood and its components:  transport and distribution of essential nutrients to tissues  removal of waste products  defense against internal insult

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Blood: Cells and Plasma Proteins Beth A. Bouchard BIOC 212: Biochemistry of Human Disease

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  1. Blood: Cells and Plasma Proteins Beth A. Bouchard BIOC 212: Biochemistry of Human Disease Spring 2005

  2. I. Major functions of blood and its components:  transport and distribution of essential nutrients to tissues  removal of waste products  defense against internal insult  repair of damaged tissues II. Two major components of blood: liquid phase and formed elements

  3. Plasma - blood treated with anticoagulants to prevent clot formation then centrifuged to remove the cellsSerum - blood that is allowed to form a fibrin clot then centrifuged to remove the cells and the clot Plasma “Buffy coat” Red blood cells Plasma Buffy coat Red blood cells

  4. Red Blood Cells (Erythrocytes)  1011 produced per day  Anucleate  Lack intracellular organelles (incapable of protein synthesis and repair)  Contain specific proteins and ions  Transport oxygen, and remove CO2 and H+  Finite life span of 60-120 days before being destroyed in the spleen

  5. Platelets •  2-3 mm in diameter •  150-400 x 106/mL blood • Normal subcellular structures except they lack a nucleus • Capable of mitochondrial protein synthesis •  Platelet function is dependent upon their activation •  Involved in blood clotting • Contain secretory organelles called alpha-granules, which contain proteins important in blood clotting • Circulate for 10 days before being destroyed

  6. Plasma proteins • Synthesized by liver or produced by plasma (B) cells • Albumin • Transferrin • Ceruloplasmin • Enzymes – coagulation enzymes, complement factors • C-reactive protein – acute phase reactant • Immunoglobulins – humoral immunity Transport proteins

  7. ALBUMIN 66 kDa • Accounts for ~50% of the total plasma protein and ~ 50% of the total liver protein production •  Half-life ~ 20 days •  Highly polar •  At pH 7.4 it is anionic with 20 negative charges per molecule

  8. Functions of Albumin  Transport of long chain fatty acids & sterols  Transport of bilirubin  Binding and solubilization of drugs

  9. Regulation of colloidal pressure Decreases in albumin concentration cause edema Gaw: Clinical Biochemistry; Churchill Livingstone (1999), p. 44.

  10. Causes of decreased plasma albumin: • Decreased synthesis • A. malnutrtion • B. malabsorption • C. advanced chronic liver disease • II. Abnormal distribution or dilution • A. overhydration • B. increased capillary permeability like in • septicemia • Abnormal excretion or degradation • A. nephrotic syndrome • B. burns • C. hemorrhage • D. certain catabolic states • E. protein losing enteropathies • Rare congenital defects • A. hypoalbuminemia • B. analbuminemia

  11. TRANSFERRIN • Transports iron in plasma as ferric ions (Fe3+) – each transferrin molecule binds 2 Fe3+ • Protects the body against the toxic effects of free iron • Normally 30% saturated with Fe3+ - increased or decreased saturation is indicative of iron overload or deficiency, respectively •  Decreased in inflammatory states due to excessive degradation of transferrin- Fe3+ complexes

  12. CERULOPLASMIN • Major copper transport protein  Regulates oxidation-reduction, transport and utilization of iron • Increased concentrations are found in active liver disease or tissue damage • Decreases are sometimes observed in individuals with Wilson’s disease

  13. ENZYMES  Enzymes of the coagulation and complement cascade have a defined function in blood  Others reside elsewhere in the body and appear incidentally in the blood – their measurement is of diagnostic value Creatine kinase Alanine aminotransferase Acid phosphatase Amylase

  14. C-REACTIVE PROTEIN (CRP) •  Major component of the acute phase response and a marker of bacterial infection •  Mediates the binding of foreign polysaccharides, phospholipids and complex polyanions, as well as the activation of complement •  <1 mg/mL in normal plasma • Slightly elevated levels of CRP are indicative of chronic, low-grade inflammation and have been correlated with an increased risk of cardiovascular disease

  15. IMMUNOGLOBULINS • Proteins produced and secreted by B cells specific for the foreign particle that stimulated their synthesis • Five classes of Ig • Multiple myeloma: arises from the aberrant proliferation of a single B cell. Light chains of Igs are produced in excess of heavy chains = paraproteins. • Elevated serum protein levels are usually due to an increase in the Ig fraction and may indicate the presence of a paraprotein.

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