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Serum in Blood Structure Composition and Role

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What is Serum in Blood Definition Composition and Difference from Plasma

Serum is a byproduct of blood clotting, in which the plasma protein fibrinogen is converted to fibrin and left behind in the clot. Antiserum - that is prepared from the blood of humans or animals that have been exposed to a disease and have developed specific antibodies, can be used to protect the persons against disease that they have been exposed to.

Study of Serum

Blood is a fluid connective tissue that travels throughout the body by transporting necessary oxygen, nutrients, and metabolic wastes. Also, it is involved in the regulation of the temperature and pH levels of the body by interacting with acids and bases.


Primarily, blood is composed of WBC (white blood cells), RBC (red blood cells), serum, and plasma. Serum and plasma are the primary components of blood and they are routinely used in blood group test experiments for determining the blood group of the patients.


The study of serum is called serology. Serum is used in many diagnostic tests and blood typing as well. Measuring the concentration of different molecules may be useful for several applications, such as determining the therapeutic index of a drug candidate in the clinical trial.


To obtain the serum, a blood sample is allowed to clot (which is called coagulation). Then, the sample is centrifuged to remove the blood cells and clot, and the resulting liquid supernatant is called the serum.

Clinical and Laboratory Uses

Serum from convalescent patients successfully recovering (or having already recovered) from an infectious disease can be used as a biopharmaceutical in the care of other people with the same disease because the antibodies formed by successful recovery are pathogen's potent fighters. Such convalescent serum (which is antiserum) is a form of immunotherapy.


Also, serum is used in protein electrophoresis, because of the lack of fibrinogen that can cause false results.


Fetal bovine serum (FBS) is very rich in growth factors and is frequently added to the growth media used for eukaryotic cell culture. The embryonic stem cells were originally maintained with a cytokine leukaemia inhibitory and an FBS combination factor, but concerns about batch-to-batch differences in FBS led to the production of serum substitutes.

Key Terms

  • Electrolyte: Any of different ions (such as chloride or sodium) that regulate the electric charge on the cells and flow of the water across their membranes

  • Interstitial fluid: In multicellular species, interstitial fluid is a solution contained in tissue spaces that inundates and moistens the cells.

  • Viscosity: It's a measurement of the force per unit area resisting uniform flow in a fluid.

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The above figure shows the blood sample after the centrifugation: The liquid components of the blood, known as plasma (the yellow section) may be separated from the erythrocytes (the red section) and platelets (the white section) by using spinning or centrifuging the blood.

Purification Strategies

Plasma and blood serum meaning are some of the largest sources of biomarkers, whether for therapeutics or diagnostics. Its huge dynamic range, further complicated by the presence of salts, lipids, and the post-translational modifications, and multiple mechanisms of degradation as well, presents the challenges in analytical reproducibility, resolution, sensitivity, and potential efficacy.


For analysis of the biomarkers in blood serum samples, it is possible to perform a pre-separation by a free-flow electrophoresis, which usually consists of a depletion of the serum albumin protein. This particular method enables a greater penetration of the proteome via separation of a variety of chargeable or charged analytes, ranging from small molecules to the cells.

Usage Note

As several other mass nouns, the term serum may be pluralized when used in certain senses. Physicians often use the term sera to refer to multiple serum specimens from multiple individuals (each with its own population of antibodies) (Latin plural, as opposed to as serums).

Enzymes That Test for in the Blood Serum

Usually, enzymes which enter the bloodstream signify something bad, whether it’s myocardial infarction, congenital heart disorders, cancer, and more. The below listed ones are some we'd find and what they exactly mean:

  • Alanine Aminotransferase (ALT; also known as SGPT)

  • Aspartate Aminotransferase (AST; also known as SGOT)

  • A liver enzyme. Can increase when using the cholesterol-lowering medications

A liver enzyme, which is released into the bloodstream following injury or even death of cells. Increased AST is seen with myocardial infarction (MI), liver diseases, and a few medications. Can increase when using cholesterol-lowering medications.

Creatinine (Cr)

Creatinine becomes elevated with kidney disease, illness, muscle injury and a few medications.

Lactate Dehydrogenase (LDH)

LDH is given as an enzyme released in the blood with cell injuries. Often, it is used as a late marker to detect heart attacks. Kidney and liver disease, megaloblastic and pernicious anemias, progressive muscular dystrophy, malignancy, and pulmonary emboli all cause an increase.

Myoglobin (Mb)

Myoglobin is given as a protein found in certain muscle types. Elevated myoglobin can indicate inflammation or muscle injury.

Troponin T (cTNT)

Troponin T is given as a protein found in the blood and it is related to the heart muscle contraction. Troponin T is valuable to detect heart muscle damage and risk.

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FAQs on Serum in Blood Structure Composition and Role

1. What is serum in biology?

Serum is the clear, straw-colored liquid portion of blood that remains after clotting factors have been removed. It is obtained after blood coagulates and the clot is separated, leaving a fluid that lacks fibrinogen and most clotting proteins.

  • Contains water, electrolytes, hormones, antibodies, and proteins
  • Does not contain blood cells or clotting factors
  • Commonly used in diagnostic laboratory tests

2. What is the difference between serum and plasma?

The main difference between serum and plasma is that serum lacks clotting factors, while plasma contains them. Plasma is the liquid component of blood before clotting and contains fibrinogen, whereas serum is obtained after clot formation.

  • Plasma: Contains clotting proteins; collected using anticoagulants
  • Serum: Lacks fibrinogen; collected after blood clots
  • Both contain nutrients, hormones, and antibodies

3. How is serum obtained from blood?

Serum is obtained by allowing blood to clot and then separating the liquid portion from the clot. The standard steps include:

  • Collect blood without anticoagulant
  • Allow it to clot at room temperature
  • Centrifuge the sample to separate the blood clot
  • Collect the clear supernatant fluid, which is serum
This process removes clotting proteins and blood cells.

4. What are the main components of serum?

Serum mainly consists of water, proteins, electrolytes, hormones, and antibodies. Its major components include:

  • Water (about 90%)
  • Albumin and globulins
  • Antibodies (immunoglobulins)
  • Electrolytes such as sodium and potassium
  • Hormones, enzymes, and waste products
It does not contain fibrinogen or blood cells.

5. What is the function of serum in the body?

Serum functions mainly in transport and immune defense within the body. Its key roles include:

  • Transporting hormones and nutrients
  • Carrying antibodies for immune protection
  • Maintaining osmotic pressure through albumin
  • Distributing electrolytes and metabolic waste
Although clotting factors are removed, serum still supports many physiological processes.

6. Why is serum used in laboratory tests?

Serum is widely used in laboratory tests because it is free of clotting factors that could interfere with biochemical analysis. It is ideal for measuring:

  • Blood glucose
  • Cholesterol
  • Hormone levels
  • Antibody titers
Its clear composition allows accurate diagnostic testing in clinical biochemistry and immunology.

7. What are serum antibodies?

Serum antibodies are immunoglobulins present in serum that help identify and neutralize pathogens. These immunoglobulins (IgG, IgM, IgA, IgE, IgD) are produced by B lymphocytes.

  • Bind to specific antigens
  • Neutralize bacteria and viruses
  • Activate the complement system
They play a central role in adaptive immunity.

8. What is antiserum?

Antiserum is serum that contains specific antibodies against a particular antigen. It is produced by immunizing an animal or person with an antigen and then collecting the antibody-rich serum.

  • Contains high levels of specific antibodies
  • Used in passive immunity
  • Applied in treatments like antivenom therapy
Antiserum provides immediate but temporary protection.

9. Can serum be used for vaccination?

Serum itself is not a vaccine, but antibody-containing serum can provide passive immunity. Unlike vaccines, which stimulate active immune responses, injected antiserum:

  • Provides ready-made antibodies
  • Offers immediate protection
  • Does not produce long-term immune memory
This method is called passive immunization.

10. What is fetal bovine serum (FBS) used for?

Fetal bovine serum (FBS) is a nutrient-rich serum used to support cell growth in laboratory cell culture. It is derived from fetal cow blood and contains:

  • Growth factors
  • Hormones
  • Attachment factors
  • Essential nutrients
FBS is commonly added to culture media to promote proliferation of mammalian cells in research and biotechnology.


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