MP Board · Class 12 · Chemistry · BiomoleculesWhat are nucleic acids? Differentiate between DNA and RNA in detail, explaining their chemical composition, structural differences, and biological functions.

Definition of Nucleic Acids\nNucleic acids are long-chain polymers of nucleotides, which are responsible for the transmission of hereditary characteristics and protein synthesis in living organisms. They are mainly of two types: DNA (Deoxyribonucleic acid) and RNA (Ribonucleic acid).

Chemical Composition\nA nucleotide consists of three chemical components:

1. Pentose Sugar: DNA contains $\beta$-D-2-deoxyribose, whereas RNA contains $\beta$-D-ribose.
2. Nitrogenous Bases:
   • Purines: Adenine (A) and Guanine (G) are present in both DNA and RNA.
   • Pyrimidines: Cytosine (C) and Thymine (T) are present in DNA, while Cytosine (C) and Uracil (U) are present in RNA.
3. Phosphoric Acid: $\text{H}_3\text{PO}_4$ molecule which forms phosphodiester linkages.

Detailed Differences between DNA and RNA

1. Sugar Component:
   • DNA contains 2-deoxyribose sugar.
   • RNA contains ribose sugar.
2. Pyridine Bases:
   • DNA contains Adenine, Guanine, Cytosine, and Thymine.
   • RNA contains Adenine, Guanine, Cytosine, and Uracil.
3. Structure:
   • DNA has a double-helix structure where two strands coil around each other.
   • RNA is usually a single-stranded molecule, which sometimes folds back on itself.
4. Function:
   • DNA is responsible for heredity, storing genetic information from generation to generation.
   • RNA is primarily involved in protein synthesis.
5. Stability:
   • DNA is chemically more stable and resists hydrolysis.
   • RNA is less stable and easily hydrolyzed by alkalies.