Plasma Proteins: Structure, Function, and Classification

Plasma Composition

• Plasma is the non-cellular portion of blood.
• Total plasma protein level ranges from 6-7 gm/dl.

Types of Plasma Proteins

• There are two main categories of plasma proteins: albumin and globulin.

Albumin

• Albumin is not precipitated by half-saturated ammonium sulfate.
• Albumin constitutes over half of the total protein.
• Albumin level ranges from 3.5-5.5 gm/dl.
• Albumin is a simple protein and a single entity.

Globulin

• Globulin is precipitated by half-saturated ammonium sulfate.
• Globulin level ranges from 2-3 gm/dl.
• Globulin is a complex protein with many components.
• Subglobulins (α1, α2, β, and γ-globulins) are detected as bands on electrophoresis.

Age-Related Changes

• After the age of 40, albumin levels gradually decline, and globulin levels increase.

Electrophoresis

• Electrophoresis is used to separate and identify plasma proteins.
• The electrophoretic pattern is shown in Fig. 1a.
• Different plasma protein bands are semi-quantitated using a densitometer (Fig. 1b).