Albumin - Definition and Overview

You may be looking for albumen, or egg white.

Albumin is a blood plasma protein that is produced in the liver and forms a large proportion of all plasma protein.

The normal range of albumin concentrations in human blood is 3.5 to 5.0 g/dL, and albumin normally constitutes about 60% of plasma protein; all other proteins present in blood plasma are referred to collectively as globulin. Albumin is essential for maintaining the oncotic pressure needed for proper distribution of body fluids between intravascular compartments and body tissues. albumin is negatively charged. the glomerular basement membrane is also negatively charged, this prevents the filtration of albumin in the urine. In nephrotic syndrome, this property is lost, and there is more albumin loss in the urine.

Because smaller animals (for example rats) function at a lower blood pressure, they need less oncotic pressure to balance this, and thus need less albumin to maintain proper fluid distribution.

Functions of albumin:

• Maintains oncotic pressure
• Transports thyroid hormones
• Transports other hormones, particularly fat soluble ones
• Transports fatty acids ("free" fatty acids)
• Transports unconjugated bilirubin
• Transports many drugs
• Competitively binds calcium ions (Ca²⁺)
• Buffers pH

Causes of albumin deficiency:

• Cirrhosis of the liver (most commonly)
• Decreased production (as in starvation)
• Excess excretion by the kidneys (as in nephrotic syndrome)
• Excess loss in bowel (protein losing enteropathy)

Links

• Human albumin structure in the Protein data bank [1] (http://www.rcsb.org/pdb/cgi/explore.cgi?pid=52421101802426&page=0&pdbId=1AO6)