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Plasma vs Serum: Understanding the Crucial Differences in Blood Components

Introduction to Serum and Plasma

Blood is one of the most crucial components of our body’s life-supporting system. It consists of various elements, including red blood cells, white blood cells, plasma, and serum.

While many of us are familiar with blood as a whole, few of us possess an in-depth understanding of its individual components. This article seeks to enlighten its readers on two of these components: serum and plasma.

We will be exploring their definition, composition, properties, and use in diagnostic and therapeutic scenarios.

Definition and Composition of Serum and Plasma

To understand serum and plasma, we must first understand the liquid portion of human blood, which is called plasma. Plasma is a yellowish-colored fluid that makes up approximately 55% of blood, while the other 45% is made up of red and white blood cells, collectively known as formed elements.

Plasma is composed of 92% water and 8% dissolved solutes, including electrolytes, proteins, hormones, and nutrients. Serum, on the other hand, is the fluid that is left after the clotting factors are removed from the plasma.

It is an amber-colored, watery liquid that lacks blood cells, fibrin, and other clotting factors, making it thinner than plasma. However, like plasma, serum contains a variety of proteins, electrolytes, and other biomolecules.

In summary, the difference between plasma and serum is that plasma still contains clotting factors, while serum does not. Both plasma and serum,s are composed of water, electrolytes, proteins, hormones, and microorganisms.

In addition, they also contain unique elements that give them their diagnostic and therapeutic properties.

Diagnostic and Therapeutic Uses of Serum and Plasma

One of the most critical diagnostic uses of serum and plasma is in serological testing, which seeks to detect the presence of antibodies in the blood. Such tests are used to diagnose various diseases, including viral infections like HIV, hepatitis, and bacterial infections such as Lyme disease.

By testing the presence of antibodies in serum, the body’s immune response can be monitored and interpreted for diagnostic and therapeutic purposes. Another crucial use of serum is its therapeutic application.

Serum can be used as antivenom or antitoxin. For example, snake venom can be toxic and cause deadly side effects in individuals who have been bitten.

However, serum from animals that have been immunized against this venom can be administered to such individuals to counteract its effects. Serum may also be used for transfusion therapy in patients who have lost large volumes of blood.

In such cases, serum can be used as a temporary substitute for whole blood to restore fluids and electrolytes while the body regenerates its blood cells.

Properties and Use of Serum

As previously mentioned, serum is an amber-colored, watery liquid that is protein-rich and lacks blood cells and clotting factors. It contains essential elements such as albumin, globulin, and antibodies that play a crucial role in the immune system.

One of the most significant uses of serum is in enzyme tests and hormone tests. Enzymes are biomolecules that facilitate metabolic processes in the body.

When metabolized, enzymes release specific by-products that can be detected in the blood. Similarly, hormones are chemical messengers secreted by glands or specialized cells that regulate various bodily functions.

By measuring the levels of these biomolecules in the serum, doctors can diagnose and monitor specific conditions in the body. Serum must also be appropriately stored to prevent contamination or degradation.

It should be stored at -20C for long-term preservation, which helps maintain the protein composition at optimal levels. At higher temperatures, enzymes and other biomolecules can degrade, affecting the reliability of diagnostic test results.


Serum and plasma are two critical components of human blood with unique properties and uses. Understanding their composition, properties, and diagnostic and therapeutic applications is crucial in maintaining a healthy body.

Through this article, we hope to have shed some light on these essential blood components and their roles in our body. With further research and development, the uses of serum and plasma in diagnostic and therapeutic scenarios will continue to expand, saving lives and improving overall healthcare.

The Difference Between Serum and Plasma

Blood is a vital fluid that keeps our body’s tissues nourished and alive. It consists of two primary components: formed elements and blood plasma.

Plasma is the liquid component of blood composed of water, electrolytes, proteins, hormones, and other solutes that fill the spaces between the formed elements. It plays a critical role in maintaining the body’s pH, exchanging minerals, and transporting or dissolving vital substances.

Serum and plasma are two distinct components of blood. Though similar, they differ in some ways that are essential to understand.

In this article, we’ll dive deeper into the differences between blood serum and plasma, including their composition, characteristics, and medical uses.

Definition and Properties of Plasma

Plasma is the largest component of the blood, occupying about 55% of the total blood volume. It is a straw-colored, clear, and slightly viscous fluid that consists mainly of water, electrolytes, dissolved proteins, glucose, clotting factors, hormones, carbon dioxide, and other nutrients.

In addition, plasma acts as a transport medium for oxygen, carbon dioxide, and other waste products throughout the body. Plasma serves an essential function in maintaining blood pressure, preventing edema, and helping to maintain body temperature.

It is also a reservoir of clotting factors essential for hemostasis, the process through which the body seals broken blood vessels to prevent hemorrhage.

Use and Storage of Plasma

Plasma is used in a variety of medical applications. Trauma patients, for example, may require transfusions of fresh-frozen plasma to restore clotting factors lost through blood loss.

In individuals with liver disease or clotting factor deficiencies, plasma therapy can help maintain hemostasis. Additionally, plasma can be used as an anticoagulant, as it contains heparin, which can inhibit blood clots formation.

To preserve plasma’s integrity, the fluid must be stored at -18C or lower. Careful handling can ensure that the plasma remains viable for up to one year.

Additionally, anticoagulants such as sodium citrate can help preserve plasma, allowing it to be safely frozen and stored for future use.

Definition and Properties of Serum

Serum is the yellowish liquid that remains after the blood has clotted and the formed elements like red blood cells and clotting factors have formed a solid structure. Unlike plasma, serum does not contain clotting factors, as they have been utilized in the bloodstream.

Thus, serum is a protein-rich fluid that contains enzymes, albumin, globulin, immuno-globulins, and other proteins. Serum also contains electrolytes, hormones, and other biomolecules important for diagnosis and treatment.

In particular, serum is used in enzyme tests and hormone level monitoring, as the biomolecules in serum reflect metabolic and hormonal activity in the body. Serum is also directly used for plasma transfusion or as an alternative fluid in blood loss.

Use and Storage of Serum

Serum is an essential biomarker for diagnosing medical conditions such as liver disease and tumors, inflammation, and metabolic disorders. It can also be used in hormone assays, and therapeutic applications such as plasma transfusion, due to its nutrient-rich composition and unique protein profile.

Serum should be stored carefully to maintain its composition and prevent contamination. It can be safely frozen at -20C or lower and is viable for up to five years with proper preservation techniques.

Various components in serum can rapidly degrade at higher temperatures, leading to the loss of biomarker information or clinical activity.

The Separation and Acquisition of Serum and Plasma

Plasma and serum are separated from whole blood through different methods based on their properties. Coagulation is required to obtain serum while plasma can be obtained through anticoagulation.

Coagulation is a naturally occurring process in which proteins in blood come together to form a solid barrier which traps blood cells and stops blood flow over an open wound, for instance. This process can also separate serum from the whole blood, by labelling the plasma clot that contains the formed elements.

Once the clot has been formed and removed, the remaining liquid is serum. Plasma, on the other hand, requires anticoagulants (like EDTA, heparin, or citrate) to prevent coagulation.

Centrifugation is then used to separate any remaining solid components from the fluid, resulting in a clear, fluid mixture of proteins, sugars, and other biomolecules named plasma.

Characteristics of Plasma and Serum

Plasma and serum differ in their composition and characteristics such as density and water content. Plasma is denser than serum, as it contains fibrinogen and other clotting factors among its proteins.

On the other hand, Serum lacks fibrinogen, which has been used in the circulatory system to help clot formation, and other clotting factors, so it has a slightly lower density than Plasma. Plasma contains more water than Serum owing to its higher percentage of dissolved solutes such as proteins and electrolytes.

In contrast, Serum contains more proteins and other molecules such as enzymes, particularly liver enzymes and hormones.


Overall, serum and plasma are two crucial components of blood that play different but critical roles in maintaining the body’s homeostasis. Plasma and serum differ in their chemical composition, properties, and medical applications.

Correctly identifying and using these components in diagnosis and treatment can lead to more precise diagnoses and better treatment outcomes. Though quite similar, the differences between plasma and serum require attention in their collection, storage and usage.

In conclusion, understanding the difference between plasma and serum is vital to the accurate identification and treatment of medical conditions. Plasma is the liquid component of blood and contains clotting factors, while serum is the fluid remaining after coagulation without fibrinogen and other clotting factors.

Both plasma and serum are utilized for diagnostic and therapeutic purposes, particularly in enzyme and hormone tests and transfusion therapy. Proper storage techniques are crucial for preserving their integrity and effectiveness.

Maintaining a clear knowledge of the complexities of blood and its components is essential for optimal medical care.

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