Introduction to BioChemistry

The study of all the molecules making up the body of living beings and all the chemical processes occurring in the body is termed as biochemistry.

Some important bio-molecules are Carbohydrate, protein, lipids and nucleic acid. These bio-molecules together constitute the whole body of living organism. These are made and breakdown in the body by different chemical reactions by the process called metabolism.

Carbohydrate Metabolism

Monosaccharides containing an aldehyde group are called aldoses and those with a keto group are called ketoses. Disaccharides, oligosaccharides, and polysaccharides consist of monosaccharides linked by glycosidic bonds

 Salivary α-amylase acts on dietary polysaccharides, producing oligosaccharides. Pancreatic α-amylase continues the process of polysaccharide digestion. The final digestive processes occur at the mucosal lining of the small intestine. They produce monosaccharides. Absorption of the monosaccharides is carried out by specific transporters present in intestinal mucosal cells.

Various metabolic processes involving carbohydrates mainly glucose are Glycolysis , Tricarboxylic Acid Cycle,  Gluconeogenesis, Glycogen Metabolism , Metabolism of Monosaccharides and Disaccharides , Pentose Phosphate Pathway and production of Glycosaminoglycans, Proteoglycans, and Glycoproteins

Protein metabolism

Proteins are the most abundant and functionally diverse bio-molecules. Virtually every life process depends on them. For example, enzymes and polypeptide hormones direct and regulate metabolism in the body, whereas contractile proteins in muscle allows movement. The protein collagen gives bones firmness. Hemoglobin and plasma albumin present in bloodstream, help transport molecules essential to life, whereas immune-globulins fight infectious bacteria and viruses. Proteins are diverse in functions, yet all have same structural feature of being linear polymers of amino acids. 

The metabolic processes involving protein subunits include amino acids disposal of nitrogen, amino acid degradation and synthesis and conversion of amino acids to specialized products. Proteins are synthesized by transcription of DNA to mRNA followed by translation of mRNA to amino acid chain. These amino acids then fold to give rise to proteins.

Lipid metabolism

Lipids are a heterogeneous group of hydrophobic  organic molecules that are water insoluble. Because of their insolubility in aqueous solutions, body lipids are generally found compartmentalized, as in the case of membrane-associated lipids, or transported in plasma in association with protein, as in lipoprotein particles , or on albumin. Lipids are a major source of energy for the body, and they also provide the hydrophobic barrier that permits partitioning of the aqueous contents of cells and subcellular structures. Lipids serve additional functions in the body, for example, some fat-soluble vitamins have regulatory or coenzyme functions, and the prosta glandins and steroid hormones play major roles in the control of the body’s homeostasis.

The metabolic processes include metabolism of dietary lipids, fatty acid and triacylglycerol metabolism, complex lipid metabolism and cholesterol and steroid metabolism.

Nucleic acid metabolism

Nucleic acids are necessary for the storage and expression of genetic information. There are two types of nucleic acids: deoxyribonucleic acid (DNA) and ribonucleic acid(RNA). DNA, the repository of genetic information, is present in chromosomes in the nucleus of eukaryotic organisms. The genetic information found in DNA is copied and transferred to daughter cells through the process called DNA replication. RNA synthesis also known as ‘Transcription’ is the first stage in the expression of genetic information. Next, the code contained in the nucleotide sequence of messenger RNA molecules is used to synthesize proteins in a process called ‘Translation’, thus completing gene expression. The flow of information from DNA to RNA to protein is called “central dogma” of molecular biology. Gene expression is regulated at every step by different checkpoints and repertoire other molecules to provide additional control over the kinds and amounts of functional products that are produced.


Vitamins are chemically unrelated organic compounds whose needed amount cannot be synthesized by humans therefore they must be supplied by the diet. There are 2 types of vitamins.1.  water-soluble vitamins include 9 vitamins (folic acid, cobalamin, ascorbic acid, pyridoxine, thiamine, niacin, riboflavin, biotin, and pantothenic acid) 2. fat-soluble Vitamins including  vitamins A, D, K, and E. They are required to perform specific cellular functions, for example, many of the water-soluble vitamins are precursors of coenzymes for the enzymes of intermediary metabolism. In contrast to the water-soluble vitamins, only one fat soluble vitamin (vitamin K) has a coenzyme function. These vitamins are released, absorbed, and transported with the fat of the diet. They are not readily excreted in the urine  and significant quantities are stored in the liver and adipose tissue.