Second lecture

Plasma proteins 2-Globulins: (2.7%)   globulins and  globulins: –Transport lipids and fat soluble vitamins.   globulins: –Antibodies.

Plasma proteins Synthesis Synthesis –In lymphocytes (T and B) –Made in response to presence of antigen ( “ foreign ” macromolecule, virus particle etc.) Functions Functions –Primary function is antigen binding (immune response) –Secondary function is complement binding (after antigen) 2-Globulins: (2.7%)

Classes of Immunoglobulins IgG: Microorganisms identification & engulfment. IgG: Microorganisms identification & engulfment. IgE: Inhibits parasite invasion; involved in allergic reactions. IgE: Inhibits parasite invasion; involved in allergic reactions. IgA: IgA: Passive immunity provided by breast milk. Passive immunity provided by breast milk. Agglutinates infectious agents in secretions outside the body. Agglutinates infectious agents in secretions outside the body. Present in tears & mucous. Present in tears & mucous. IgM: Microorganisms identification & engulfment. IgM: Microorganisms identification & engulfment.

Plasma proteins 3-Fibrinogen: (0.3%) Structure Structure –MW –Sequence of amino acids is known (3000)  6 polypeptide chains, 2  (67,000), 2  (56,000), 2  (47,000) Coagulation Coagulation

separation of plasma proteins 1-Size Exclusion Chromatography (SEC) 1-Size Exclusion Chromatography (SEC) –Porous matrix (sephadex). 2-Affinity chromatography 2-Affinity chromatography –molecule attached to a column that specifically binds the protein of interest.  Coenzyme / enzyme  Antigen / Antibody 3-SDS-PAGE (polyacrylamide gel electrophoresis) 3-SDS-PAGE (polyacrylamide gel electrophoresis) –Separates by size. –Proteins are complexed with SDS to give the same charge density.

Zone Electrophoresis of Plasma Proteins globulinsalbumin  

separation of plasma proteins 4-Precipitation by salts: 4-Precipitation by salts: - Albumin is separated by full saturation with ammonium sulphate. - Albumin is separated by full saturation with ammonium sulphate. -Globulins are precipitated by half saturation with ammonium sulphate. -Globulins are precipitated by half saturation with ammonium sulphate. 5-Ultra centrifugation: 5-Ultra centrifugation: - Plasma proteins can be separated according to their different rates of sedimentations. - Plasma proteins can be separated according to their different rates of sedimentations. -The sedimentation rate depends on weight, shape of the molecule & density of suspending medium. -The sedimentation rate depends on weight, shape of the molecule & density of suspending medium.

Functions of Plasma Proteins Maintenance of: Maintenance of:  Colloid osmotic pressure.  pH.  electrolyte balance. Transport of: ions, fatty acids, steroids, hormones etc. Transport of: ions, fatty acids, steroids, hormones etc.  Albumin (fatty acids), ceruloplasmin (Cu 2+ ), transferrin (Fe), lipoproteins (LDL, HDL).

Functions of Plasma Proteins Nutritional: source of amino acids for tissues. Nutritional: source of amino acids for tissues. Hemostasis: (coagulation proteins). Hemostasis: (coagulation proteins). Prevention of thrombosis: (anticoagulant proteins). Prevention of thrombosis: (anticoagulant proteins). Defense against infection: (antibodies, complement proteins). Defense against infection: (antibodies, complement proteins).

 Assembly time on ribosome ~ 1-2 min.  t 0.5 in circulation - 19 days. 14 g lost per day. 14 g lost per day. 0.4 mg synthesized per hour per g of liver. 0.4 mg synthesized per hour per g of liver. Synthesis of plasma proteins  All albumin, all fibrinogen and most of the globulins (50-80%) (alpha & beta) are formed in the liver.  The remaining part of globulins (gamma) are formed in the lymphoid tissues.

Plasma proteins circulate not only inside the vascular system but also across the capillary bed into the interstitial fluid and back into the plasma through lymphatic vessels. Plasma proteins circulate not only inside the vascular system but also across the capillary bed into the interstitial fluid and back into the plasma through lymphatic vessels. Catabolism of plasma proteins  Tissue macrophages take up albumin by pinocytosis.  Albumin is broken down within the lysosomes of tissue macrophages to amino acids.