9Proteins are the molecules that accomplish most of the functions of living cell. They make possible all the chemical reactions in the cell by acting as Enzymes that promotes specific chemical reactions, which would occur otherwise so slowly as to be negligible. If proteins are the workhorses of biochemical world, nucleic acids are the drivers; All the genetic information in any living creature is stored in Deoxyribonucleic acid (DNA) and Ribonucleic acid (RNA), which are polymers of four simple nucleic acid units, called nucleotides. There are four nucleotides found in DNA. Each nucleotide consist of three parts: one of two base molecules (a purine & a pyramidine), plus a sugar (ribose in RNA and deoxyribose in DNA) and one or more phosphate groups. The purine nucleotides are Adenine (A) and Guanine (G) and the pyramidine nucleotides are Cytosine (C) and Thymine (T). Nucleotides are also called basis and since, two DNA consist of two complementary strands bonded together, these units are often called base pairs. The nucleotides are linked to each other in the polymer by phophodiester bonds. This bond is directional. A strand of DNA has a Head ( called 5’ end) and a tail( called 3’ end).
One of the property of DNA is that it forms a double helix i.e. two helical strands of polypeptide, running in opposite directions, held together by hydrogen bonds. Adenine bond exclusively with thymine and Guanine with cytosine because of these bonding rules the sequence of in complementary strand is completely determined.
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