Total protein is a rough measure of serum protein. Protein measurements can reflect nutritional state, kidney disease, liver disease, and many other conditions. If total protein is abnormal, further tests must be performed to identify which protein fraction, and then which specific protein, is abnormal.
Proteins are important constituents of all cells and tissues. Proteins are made from amino acids. There are many different kinds of proteins in the body with many different functions. Enzymes, some hormones, hemoglobin (oxygen transport), LDL (cholesterol transport), fibrinogen (blood clotting), collagen (structure of bone and cartilage), immunoglobulins (antibodies) are some examples of proteins.
Serum proteins are grossly separated into albumin and globulins. That is, total protein equals albumin plus globulin. Globulins are roughly divided into alpha-1, alpha-2, beta, and gamma globulins.
Albumin is the protein of highest concentration in the serum (plasma is serum plus fibrinogen). Albumin is a carrier of many small molecules, but is also of prime importance in maintaining the osmotic pressure of the blood (that is, keeping the fluid from leaking out into the tissues).
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