Plasma vs Serum

Team Biology at
Created by: Team Biology at, Last Updated: July 9, 2024

Plasma vs Serum

Plasma and serum are two fundamental components of blood that play vital roles in the circulatory system of animals, including humans. Both are derived from blood but serve different purposes and have distinct characteristics. Understanding the differences between plasma and serum is crucial for medical science, diagnostics, and research, as each component is used for various tests and procedures. Let’s explore the unique features and functions of plasma and serum, highlighting their importance in health and disease.

What is the difference between plasma and serum?

Plasma is the liquid portion of blood, comprising about 55% of its volume. It is a straw-colored, watery fluid that carries blood cells, proteins, nutrients, hormones, and waste products throughout the body. Plasma plays a key role in maintaining blood pressure and volume, supplying critical proteins for blood clotting, and supporting immune responses. Serum, on the other hand, is the fluid that remains after the blood has clotted. It is essentially plasma without the clotting factors. Serum contains antibodies, hormones, and other proteins and is used in diagnostic tests to detect diseases and monitor organ function.


Plasma serves as the transport medium for the blood components, facilitating their movement throughout the body. It is akin to a river that carries boats (cells and molecules) to various destinations, ensuring that tissues receive the nutrients, hormones, and proteins they need while removing waste products. Plasma’s composition reflects its diverse roles; it is rich in proteins such as albumin, globulins, and fibrinogen, which are crucial for clotting, immune functions, and maintaining osmotic balance.

Key Characteristics of Plasma

  • Structure: Liquid and homogenous, with no cells or solid components in its natural state.
  • Location: Constitutes the majority of the blood volume, circulating throughout the entire cardiovascular system.
  • Composition: Contains water (90-92%), proteins (6-8%), and dissolved substances (e.g., electrolytes, nutrients, waste products).
  • Functionality: Transports nutrients, hormones, and proteins; regulates blood pressure and volume; maintains pH balance.


Serum is the superhero of diagnostic testing, offering a clear window into the body’s internal environment. After blood coagulation, serum emerges as a clear liquid devoid of cells and clotting proteins, making it ideal for testing as it provides a rich source of antibodies and hormones without the interference of clotting factors. Serum analysis is pivotal in diagnosing diseases, evaluating organ function, and understanding the body’s immune response to infections and vaccines.

Key Characteristics of Serum

  • Structure: Clear, cell-free liquid that separates from clotted blood.
  • Location: Obtained from blood after the clotting process, devoid of blood cells and clotting factors.
  • Composition: Rich in proteins such as albumin and globulins, excluding clotting factors.
  • Functionality: Used in diagnostic tests to assess health, detect diseases, and monitor organ function.

Exosome purification from serum and plasma

Exosome purification from serum and plasma starts with initial centrifugation to separate the liquid components from whole blood. This step is followed by low-speed spins or filtration to remove larger particles. The key step involves high-speed ultracentrifugation, which concentrates the exosomes into a pellet. Additional methods like size-exclusion chromatography may further refine the purity. The final step often includes techniques such as Western blotting to confirm the presence of exosomes in the sample.

Differences Between Plasma and Serum

Differences Between Plasma and Serum
DefinitionThe liquid portion of blood, containing water, proteins, electrolytes, nutrients, and waste products.The fluid that remains after blood has clotted, devoid of clotting factors.
Clotting FactorsContains clotting factors such as fibrinogen.Lacks clotting factors.
Cell ContentDoes not contain blood cells.Does not contain blood cells.
Use in Medical TestingUsed in tests that require clotting factors (e.g., coagulation tests).Used in a wide range of diagnostic tests, including biochemical and immunological assays.
ColorStraw-colored.Slightly clearer than plasma, due to the absence of clotting proteins.
Volume Percentage in BloodApproximately 55% of total blood volume.Varies depending on the amount of clotting; usually slightly less than plasma volume.
Protein ContentContains a wide range of proteins, including albumin, globulins, and fibrinogen.Contains albumin and globulins, but no fibrinogen.

Key Similarities Between Plasma and Serum

  1. Origin: Both come from blood. They are the liquid components left once the blood has been cleared of cellular elements like red blood cells, white blood cells, and platelets.
  2. Basic Composition: Both fluids are mainly water, making up about 90% of their composition. This high water content is crucial for their roles in carrying nutrients, hormones, and waste products throughout the body.
  3. Presence of Dissolved Elements: Plasma and serum contain dissolved gases (such as oxygen and carbon dioxide), nutrients (including glucose, fatty acids, and amino acids), hormones, and waste products. These elements are essential for various physiological processes, including respiration, nutrition, and excretion.
  4. Electrolytes: They both have similar concentrations of electrolytes, including sodium, potassium, chloride, bicarbonate, and magnesium. These electrolytes are vital for maintaining pH balance, osmotic pressure, and proper cellular function.
  5. Proteins: Apart from the clotting factors that plasma has and serum lacks, both contain a wide range of proteins, such as albumin and globulins. These proteins are crucial for maintaining osmotic balance, immune responses, and transporting substances.
  6. Function in Diagnostics: Both plasma and serum serve in medical and diagnostic laboratories to analyze the biochemical and physiological state of the body. They can provide valuable information about an individual’s health, including kidney and liver function, nutritional status, and the presence of infections or diseases.
  7. Extraction Process: The initial steps to obtain both plasma and serum involve collecting blood and using centrifugation to separate the liquid component from the blood cells.

Key Differences Between Plasma and Serum

  • Function:
    • Plasma: Serves as the medium for transporting blood cells, nutrients, hormones, and waste products throughout the body.
    • Serum: Used for diagnostic tests to detect diseases, assess organ function, and understand immune responses.
  • Clotting Factors:
    • Plasma: Contains all clotting factors, making it essential for coagulation tests.
    • Serum: Devoid of clotting factors, which are consumed during the clotting process.
  • Diagnostic Use:
    • Plasma: Utilized in tests requiring the presence of clotting factors.
    • Serum: Preferred for biochemical, immunological, and serological tests due to the absence of clotting proteins.
  • Extraction Process:
    • Plasma: Obtained by centrifuging blood with an anticoagulant, preventing clot formation.
    • Serum: Produced by allowing blood to clot naturally before centrifugation, separating the clot from the clear serum.


What is the major difference between serum and plasma?

Plasma contains clotting factors, while serum doesn’t due to clotting. Plasma is the liquid component of blood, whereas serum is plasma without clotting proteins.

Why serum is used instead of plasma?

Serum is used for certain tests to avoid interference from clotting factors present in plasma. It provides clearer results for specific diagnostic procedures.

What is the main difference between serum and plasma quizlet?

Plasma includes clotting factors, while serum does not. Plasma is the liquid portion of blood containing proteins, while serum is plasma without clotting factors.

How do you separate plasma and serum from blood?

Both are separated by centrifugation: Plasma is separated by anticoagulant-treated blood, while serum is separated from clotted blood after coagulation and centrifugation.

Can you separate plasma from blood without centrifuge?

Yes, by allowing blood to naturally clot and then using manual methods like pipetting or filtration, though less efficient and more time-consuming than centrifugation.

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