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Biochemistry of Blood

PLASMA PROTEINS Types of plasma proteins The normal total plasma protein concentration is around 6 to 8 g/dl of blood. The major forms of plasma proteins are: 1. Albumin constitutes around 60% of all the plasma proteins (3.5–5 g/dl). 2. Globulins: Normal plasma concentration is 2–3 g/dl. Globulins occur in different forms: i) a-globulins ii) b-globulins iii) g-globulins 3. Fibrinogen (0.2–0.4 g/dl)

SEPARATION OF PLASMA PROTEINS Salting out technique Electrophoresis Ultracentrifugation technique Cohn's fractionation Gel filtration (molecular seiving):

Separation of serum proteins by electrophoresis (normal pattern)

ESTIMATION OF CONCENTRATIONS OF FRACTIONS OF PLASMA PROTEINS BY DENSITOMETER

FUNCTIONS OF ALBUMIN 1. Maintains colloid osmotic pressure (COP) of plasma 2. Transport function 3. Buffering action 4. Nutritional function

CLINICAL SIGNIFICANCE OF ALBUMIN Albumin by binding to certain compounds in blood prevents them from crossing the blood–brain barrier, e.g. albumin–bilirubin complex, albumin–fatty acid complex. Hypoalbuminemia Tissue edema Kwashiorkor Cirrhosis of liver Nephrotic syndrome (Continued…

CLINICAL SIGNIFICANCE OF ALBUMIN …Continues) paucialbuminuria or microalbuminuria The normal albumin–globulin ratio (A/G ratio) is about 1.2:1 to 2:1. The A/G ratio is lowered or reversed either when albumin is decreased or globulins are increased, usually observed in cirrhosis of the liver, nephrotic syndrome and multiple myeloma.

GLOBULINS Globulins constitute multiple proteins that are separated into four distinct bands (a1, a2, b and g) on electrophoresis.

Major features and functions of plasma proteins (Continued…

…Continues) Major features and functions of plasma proteins

STRUCTURE OF A HUMAN IG MOLECULE Structure of a human Ig molecule (V - variable region, C - constant region; Each heavy chain is composed of four units - VH , CH1 , CH2, CH3 while light chain consists of two units - VL, CL).

CLASSES OF IMMUNOGLOBULINS Depending on the heavy chain make up, the immunoglobulins are differentiated into five major classes. 1. Immunoglobulin G (IgG) 2. IgM 3. IgA 4. IgD 5. IgE

Major characteristics of human immunoglobulins

Multiple myeloma Bence-Jones proteins Bradshaw’s test Amyloidosis

RBC Structure RBC count – Men 4.6–6.2 million/mL – Women 4.2–5.4 million/mL Metabolism in RBC

BIOCHEMICAL BASIS OF DISEASES AFFECTING RBC Hemolytic anemias Hereditary spherocytosis hereditary elliptocytosis Hemoglobinopathies Sickle cell anemia a-thalassemia b-thalassemia Genetic deficiency of glucose-6-phosphate dehydrogenase

WBC Respiratory burst