Proteins

Importance: Enzymes, extracellular matrix, transport, antibodies
Molecular Size: Typically contains 200-300 amino acids
Synthesis: Involves transcription and translation
Structure: Varies but includes nitrogen content (~16%)
Charge and Isoelectric Point: Positive and negative charges at amino and carboxyl terminals; isoelectric point is pH where net charge is zero

Enzymes: Catalyze reactions
Hormones: Insulin, testosterone, growth hormones
Transport Proteins: Hemoglobin, albumin, transferrin
Immunoglobulins: Immune response
Structural Proteins: Collagen, keratin
Storage Proteins: Ferritin
Osmotic Force: Maintains fluid distribution; decreased protein leads to edema

Prealbumin: Transport protein for T3 and T4 hormones that binds with retinol binding protein, decreased in hepatic damage, tissue necrosis, and acute inflammation.
Albumin: Major component; migrates fastest in electrophoresis
Globulins: Various functions, including immunity
Alpha-antitrypsin

Albumin: (69 kDa) is the major protein of human plasma (3.4-4.7 g/dL). Makes up 60% of total plasma protein. About 40% is present in plasma, and the other 60% is present in extracellular space. Half life of albumin is about 20 days. Migrates fastest in electrophoresis in alkaline ph and precipitates last in salting out methods.
Colloidal Osmotic Pressure: 75-80% of osmotic pressure; regulates blood volume. Maintains blood volume and body fluid distribution. Hypoalbuminemia leads to retention of fluid in tissue spaces (EDEMA)
Transport Function: BindsFFA, calcium, hormones, drugs
Nutritive Function: Provides amino acids for protein synthesis.
Buffering Function: albumin has the maximum buffering capacity due to its high concentration and the presence of large number of histidine residues.
Viscosity: exerts low viscosity.

Edema: Hypoalbuminemia results in fluid retention in tissue spaces.
Normal Levels: 3.5-5 g/dL
Hypoalbuminemia: Linked to liver cirrhosis, malnutrition, nephrotic syndrome, burns, malabsorption, analbuminemia (congenital disorder).
Hyperalbuminemia: Fluid depletion (Haemoconcentration).

Separated by ammonium sulfate by half saturation with ammonium sulphate; Molecular weight ranges from 90,000 to 130,000
Classified in alpha, beta, and gamma globulins based on electrophoretic mobility
A1 globulins, A2 globulins, B globulins, Y globulins
Alpha and Beta Globulins are synthesized in the liver.
Y globulins are synthesized in plasma cells and B cells of lymphoid tissues (Reticulo-endothelilal system)
Synthesis of Y globulins is increased in: chronic infections, chronic liver diseases, auto-immune diseases, leukemias, lymphomas.

Alpha Globulins: are glycoproteins and are subclassified in to a1 and a1 globulins based on electrophoretic mobility. (e.g. A1 antitrypsin, Orosomucoid (A1 acid glycoprotein), A1 fetoprotein (AFP))

Prealbumin: Thyroxine transport; liver disease marker
Albumin: Maintains oncotic pressure; liver and kidney disease indicator
Globulins: A,B, and Immunoglobulins: Vital in defense mechanisms and transport functions.

Biuret Method: Common technique for total protein estimation
Lowry Method: Colorimetric assay for specific proteins, sensitive to certain amino acids.