What is Blood Biochemistry?

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Blood biochemistry refers to the study of blood to understand what is happening with the body. Much of blood biochemistry is closely related to molecular biology. It deals with the structures, functions and interaction of biological macromolecules, such as proteins, nucleic acid, carbohydrates and lipids, which perform many life-essential functions. 

An average adult possesses around 5-6 litres of blood which accounts for 8% of our body weight. The blood definition biology is- “ Blood is a fluid responsible for the transport of oxygen and nutrients to the cells and waste products such as carbon dioxide and excess water to the excretory organs”. 

Introduction of Blood

Blood is a fluid that transports oxygen and nutrients to the cells and carries away carbon dioxide and other waste products. Blood can be classified both as fluid and tissue. Due to the presence of a collection of specialized cells performing specific functions, it is a tissue. These cells are suspended in plasma which is a liquid matrix making the blood a fluid as well. 

The circulation of blood is responsible for the constancy of its composition. Different organs regulate the concentration of their components. In the lungs, the blood acquires oxygen and releases carbon dioxide. The kidney filters the blood by removing excess water and dissolved waste products. After absorption by the gastrointestinal tract, the nutrient substances reach various tissues via the bloodstream. The endocrine glands release their secretions directly into the bloodstream and the blood also transports these hormones to their respective sites. 

Constituents of Blood

Blood is an opaque red fluid that flows freely throughout the body. It is denser and more viscous than water. The colour characteristic of the blood is imparted by haemoglobin. When oxygenated with blood, it forms oxyhaemoglobin which brightens the colour of blood. The biochemistry chart showing the different constituents of human blood is given below. The blood composition chart is as follows- 

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1. Plasma- The liquid portion of the blood is plasma, which contains more than 90% water. Water is essential to the existence of every living cell and thus therefore the water of the plasma is freely exchangeable with body cells and other extracellular fluids which maintains the normal hydration state of all the tissues.

2. Blood Cells- Blood cells are specialized cells present in the blood that serve a particular function. The different types of Blood cells are-

  1. Red Blood Cells: Red blood cells are primarily responsible for the transportation of oxygen throughout the body tissues. It is enclosed within a thin membrane made up of complex lipids, proteins and carbohydrates in a highly organized structure. This membrane is permeable to water, carbon dioxide, glucose and urea except for haemoglobin. Haemoglobin is a protein responsible for oxygen transport. 

  2. White Blood Cells- White blood cells are nucleated and independently motile cell structures involved in the defence mechanism and reparative activity. There are three types of WBCs, each unique to its structure and function.

  • Granulocytes - These have a multilobed nucleus and contain a large number of cytoplasmic granules. These are the important mediators of inflammatory diseases. Neutrophils, Eosinophils and Basophils are three types of granulocytes present in the body. 

  • Monocytes - These are the largest cells of the blood and are capable of ingesting infectious agents. Monocytes are usually found at chronic infection sites. 

  • Lymphocytes- These are primarily responsible for the immune response against foreign substances in the body. They are commonly found in lymph nodes, spleen, tonsils, thymus and lymphoid tissues. They enter the circulation through lymphatic channels.

  1. Platelets- The blood platelets are among the smallest cells of the body. They lack a nucleus and can’t perform cell division. The function of platelets is to prevent and control bleeding. The tiny granules inside the platelets contain an important substance that performs clotting.   


The cellular composition of blood varies in different groups of the animal kingdom. An introduction of blood biochemistry gives us a proper indication of what is happening in our bodies. By studying the enzymes released by damaged cells, the problem can be localised and treated upon.

FAQ (Frequently Asked Questions)

1. Give Brief Explanation of Blood Components and Functions.

Ans- Blood is a fluid made up of plasma and blood cells that perform specific functions. These specialized blood cells have structural differences which help them in performing these functions. The various components of blood and their functions are as follows-

  • Plasma- Plasma is the liquid part of the blood responsible for exchanging water with the cells to maintain the hydration of tissues. It also transports absorbed nutrients to the various tissues of the body.

  • Red Blood Cells- These cells consist of haemoglobin and are responsible for transporting oxygen to all the tissues throughout the body.

  • White Blood Cells- White blood cells are the warriors of the body that protect us against any foreign substance. These cells are nucleated and are actively involved in defence mechanism and reparation activity.

  • Platelets- Platelets are responsible for blood clotting to prevent and control bleeding. 

2. What are the Various Uses of Blood?

Ans- The primary function of blood is to regulate the internal environment in the body. It is because of the circulating blood that makes adaptability to changing conditions possible.

  • Respiration- A constant supply of oxygen to all living cells in the body is vital, especially those of the brain, deprivation of which can cause unconsciousness and death.  

  • Nutrition- The substances required for the nutrition of the cells in the body are transported via the blood. Carbohydrates, proteins, fats, minerals, salts. Vitamins and other substances pass through the blood plasma on their way to the tissues. 

  • Excretion- Blood is responsible for carrying the waste products to the excretory organs. Carbon dioxide is removed via the lungs while kidneys filter the blood for excessive water.

  • Immunity - Cells of the blood are responsible to interact with the infectious agents, resist or destroy invading organisms and remove foreign and dead materials.

  • Temperature regulation

  • Blood Clotting