An Introduction To Biochemistry

Biochemistry is the science of chemical processes taking place within living organisms and deals with the structure and function of protein, carbohydrate, lipid and nucleic acid present in/synthesized by living organism.

Biochemistry is also sometimes called biological chemistry, in which information related to biochemical signaling and the cell metabolism that generates the energy are studied. Biochemical processes give rise to the complexity of life. The study of the chemistry pertaining to biological processes and the production of biologically active substances are examples of biochemistry.

Biochemistry has close relation to molecular biology, in which the information stored in DNA which triggers the mechanism of life is studied.

Proteins, carbohydrates, lipids and nucleic acids are the determinants of the structure of the living cells and carry out various functions that are required for existence of the cell. The existence of a cell also dependent upon the smaller molecules and chemical ions, such as metal ions, which can be inorganic in nature, which enables synthesis of proteins from the interaction of metal ion, water and amino acids.

Only six elements from total 92 elements of periodic table, carbon, hydrogen, nitrogen, oxygen, calcium, and phosphorus compose almost 99% of our body. Apart from these six major elements, the human body requires smaller quantity of abut 18 additional trace elements (minerals).


Protein, carbohydrate, lipid and nucleic acid are the four major classes of molecules in biochemistry and are known as biomelecules. Biological molecules may be polymers and monomers. Polymers are the small micromolecules (monomers) which are linked with each other to form large macromolecules, which are called polymers. Various macromolecules combine to form large complex molecules required for biological processes. DNA, RNA, protein and carbohydrate are the examples of macromolecules.


Monosaccharides (monomers) combine to form carbohydrate. Examples of monosaccharides are glucose fructose and deoxyribose.

Carbohydrates are useful for producing and storing energy as well as for storing genetic information. Sugars fall under the class of carbohydrates. Carbohydrates are the largest known biomolecules on the Earth. They are important factors in interactions and communications amongst cells.

Glucose and Fructose

Glucose and Fructose are the simplest types of carbohydrate and they are monosaccharides. Fructose is constituent of fruits which is responsible for their sweet taste.


Two monosaccharides combine to form a disaccharide. A well-known disaccharide is sucrose (ordinary sugar, called table sugar or cane sugar).

Sucrose consists of a glucose molecule and a fructose molecule joined together.

Another example of disaccharide is lactose, which combine one glucose and a galactose molecule.

Oligosaccharides and polysaccharides

Oligosaccharide (oligo means few) are the result of combination of few (three to six) monosaccharides.


Polysaccharides are formed by combination of several monosaccharides. They either can be linear chained Polysaccharides, or they can be branched Polysaccharides. Most familiar polysaccharides are cellulose and glycogen, containing repeating glucose monomers.


Cellulose is a polymer of β-D-glucose and synthesized by plants and it is the vital component of their structure. Humans cannot synthesize or digest cellulose.


Glycogen is carbohydrate found in humans and animals which they use it for energy storage. Carbohydrate is an important source of energy for humans and animals

Glucose-the main source of energy

Glucose is the main source of energy for most living beings. Polysaccharides break down to their constituent monomers. Disaccharides such as lactose or sucrose break down into their two constituents monosaccharides. Glucose undergoes metabolism through the process of glycolyis to produce energy.


Constituents of lipids are triglycerides and fatty acids. Fatty acids are considered as monomer constituents of lipids. Lipids are water insoluble compounds of biological origin such as, fatty acids, phospholipids, sphingolipids, glycolipids, and terpenoids (e.g., retinoids and steroids). Lipids may be linear aliphatic molecules or may have a ring structures. Aromatic lipids are also found in nature. Lipids are also classified as flexible and rigid lipids.

Lipids, such as phospholipids, are constituents of several pharmaceutical products, either as co-solubilisers (in parenteral infusions) or as a carrier of drug components (such as in a liposome or transfersome).

Our diet contains Lipids and essentially it is the important source of energy for us. All cooking medium, milk and milk products like butter, cheese, ghee etc. contain fats. Vegetable oils contain various polyunsaturated fatty acids (PUFA) and medium chain triglycerides (MCT) which plays important role in cholesterol metabolism and energy production. By the process of digestion in the presence of bile enzymes secreted by liver, lipids present in the foods undergo digestion within the body. The final degradation products of fats and lipids which are absorbed by the intestine are fatty acids and glycerol.


Proteins are made of very large molecules (macro-biopolymers) synthesized from monomers known as amino acids. There are 20 standard amino acids out of which eight are essential for human beings. Different amino acids combine to form peptide, polypeptide and finally the protein.

Nucleic acids

DNA is synthesized from various Nucleic acids. DNA is a very important substance which stores genetic information. Deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) are the most common nucleic acids. Nucleotides are the monomers of nucleic acids. Adenine, cytosine, guanine, thymine, and uracil are the most common nucleotides.

Thus biochemistry offers the scope of studying the very vital functions of the living beings on the earth. Biochemistry, genetics, and molecular biology combined together is a promising base for a bright future in the field of clinical diagnostics, pharmaceutical industries, industrial and agricultural (food and herbal plants), production of enzymes and drugs, fermentation industry, food and dairy industry.

In future the biochemistry will enhance the food security, health, industrial production and environmental management.