Nucleic acids arc macromoleculcs present in all living cells cither in Free State, or in combination with other substances. These are polymers consisting of units called nucleotides; they are hence called polynucleotides. Nucleic acids arc of two types depending on whether the pentose is dcoxyribosc or ribose.
1. Deoxyribonucleic Acid (DNA):
DNAs are found in the chromosomes in the nucleus of plant and animal cells. In prokaryotes also DNA, forms the chromosomes. Some viruses, especially animal viruses have it as their genetic material. Furthermore, it is also found in mitochondria of plant and animal calls and in chloroplasts of photosynthetic organisms.
2. Ribonucleic Acid (RNA):
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Mainly found in the cytoplasm of cells. There are various types of RNAs (rRNA, TRNAs, and mRNA) involved in the expression of genetic information. Pentoses: In ribonucleic acids, the sugar is ribose; in deoxyribonucleic acids it is deoxyribose.
These two sugars differ in their chemical nature on carbon 2 as shown below.
Ribose Deoxyribose
Nitrogenous base all nitrogenous bases derive from two heterocyclic bases, purine and pyrimidine. 1. Purine base
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Two principal purine bases found in deoxyribonucleic acids as well as ribonucleic acids are adenine and guanine