Which of the following is a primary function of albumin, the most abundant plasma protein?

HSSC Staff Nurse - 2015

Applied Physiology

Easy

Appeared in: HSSC Staff Nurse - 2015

Explanation

Albumin is the most abundant protein in blood plasma, constituting about 55-65% of the total.
Its primary function is to maintain colloid osmotic pressure (oncotic pressure), which regulates fluid distribution between the blood vessels and the interstitial space.
Albumin molecules are large and mostly remain within the capillaries, where they exert an osmotic force that pulls water into the circulatory system.
This action is crucial for maintaining blood volume and pressure, and it prevents excessive fluid from leaking into the body tissues.
Albumin is responsible for approximately 80% of the plasma's total colloid osmotic pressure.

Option A: Oxygen is transported by hemoglobin, a protein contained within red blood cells (erythrocytes), not by albumin in the plasma.
Option C: Blood coagulation is a complex process involving platelets and a cascade of clotting factors. Fibrinogen, another plasma protein, is converted to fibrin to form the structural basis of a clot, but albumin does not initiate this process.
Option D: Antibodies, also known as immunoglobulins, are a type of globulin protein (specifically gamma globulins). They are produced by plasma cells (differentiated B-lymphocytes) as part of the immune response.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Functions of plasma proteins as background academic context rather than a clinical decision trigger.
A key nursing assessment is checking for edema (swelling), which can be a sign of low albumin levels (hypoalbuminemia).
Conditions like severe liver disease (e.g., cirrhosis), nephrotic syndrome, and malnutrition can lead to hypoalbuminemia because the liver cannot produce enough albumin or it is lost through the kidneys.
Monitoring serum albumin levels is crucial in patients with these conditions to manage fluid balance and nutritional status.

How to Approach the Question

First, identify the key term in the question stem, which is 'albumin'.
Recall the major components of blood: red cells, white cells, platelets, and plasma.
Remember that plasma contains water, electrolytes, and proteins. The main proteins are albumin, globulins, and fibrinogen.
Systematically review the function of each major protein. Albumin is for osmotic pressure, globulins for immunity/transport, and fibrinogen for clotting.
Evaluate each option against this knowledge. 'Maintaining plasma osmotic pressure' directly matches the primary function of albumin.
Eliminate the other options by linking them to their correct components: oxygen transport to hemoglobin, coagulation to fibrinogen/clotting factors, and antibodies to globulins.

Concept Tested & Keywords

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E6 Physiology Guyton 4SAE Part 1 p. 168-170

E6 Textbook of Biochemistry for medical StudentsDM Vasudevan Part 2 — Subpart A (pp 1-239 of 478) p. 60-62