What is Serum?
Serum is the clear, straw-colored fluid that remains after blood has clotted and the clot is removed. It is often used in medical tests because it contains essential substances that reflect the health status of the body.
👉 Quick Difference:
- Plasma = Serum + Clotting Factors (e.g., fibrinogen).
- Serum = Plasma – Clotting Factors.
This means serum does not have fibrinogen or other clotting factors but still contains proteins, electrolytes, hormones, and metabolites that are vital for diagnosis.
YOU CAN START LEARNING ONLINE BY VISITING LIVE JCE MSCE CLASSES
Composition of Serum
The composition of serum is a rich mixture of water, proteins, electrolytes, hormones, metabolites, and lipids. Below are the key components:
1. Water (90–92%)
- Forms the bulk of serum.
- Acts as a solvent for nutrients, electrolytes, and proteins.
2. Proteins (6–8%)
Proteins are the most significant functional molecules in serum.
- Albumin (55–65%)
- Maintains osmotic pressure (balances water between blood and tissues).
- Transports hormones, fatty acids, and drugs.
- Globulins (α, β, γ fractions):
- α-Globulins: Transport lipids, hormones, and metal ions.
- β-Globulins: Involved in iron transport (e.g., transferrin).
- γ-Globulins: Antibodies (immunoglobulins) essential for immunity.
- Other Proteins: Enzymes such as alkaline phosphatase (ALP), alanine transaminase (ALT), and aspartate transaminase (AST), along with complement proteins important in immune defense.
3. Electrolytes
- Cations: Sodium (Na⁺), Potassium (K⁺), Calcium (Ca²⁺), Magnesium (Mg²⁺).
- Anions: Chloride (Cl⁻), Bicarbonate (HCO₃⁻), Phosphate (PO₄³⁻).
Functions:
- Regulate nerve conduction and muscle contraction.
- Maintain pH balance and fluid homeostasis.
4. Hormones
Serum contains circulating hormones such as:
- Thyroid hormones (T3, T4)
- Cortisol
- Insulin
- Growth hormone
- Reproductive hormones
These act as chemical messengers, coordinating growth, metabolism, stress response, and reproduction.
5. Metabolites & Waste Products
- Glucose: Primary energy source.
- Urea & Creatinine: Indicators of kidney function.
- Uric Acid: High levels linked to gout.
- Bilirubin: Marker of liver function and red blood cell breakdown.
6. Lipids
- Cholesterol, triglycerides, and phospholipids.
- Their measurement helps in assessing cardiovascular risk.
Clinical Importance of Serum
Serum analysis is a cornerstone of medical diagnosis. Some important applications include:
- Liver Function Tests (LFTs): Measure enzymes like ALT, AST, and bilirubin.
- Kidney Function Tests (KFTs): Assess urea and creatinine levels.
- Lipid Profile: Detects cholesterol and triglyceride abnormalities linked to heart disease.
- Electrolyte Tests: Check for imbalances affecting the heart, muscles, and nerves.
- Hormonal Assays: Diagnose conditions such as diabetes (insulin), thyroid disorders, and reproductive health issues.
Summary
Serum is an essential component of blood used widely in clinical diagnosis. It is made up of water, proteins, electrolytes, hormones, metabolites, and lipids. Each plays a vital role in maintaining health, and its analysis provides critical information for detecting diseases, monitoring organ function, and guiding treatment.
✨ Tip for Students: When revising, always remember the key difference between plasma and serum—clotting factors! This small detail is often tested in exams.
