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1 Solutions 2 Electrochemistry 3 Chemical Kinetics 4 The d-and f-Block Elements 5 Coordination Compounds 6 Haloalkanes and Haloarenes 7 Alcohols, Phenols and Ethers 8 Aldehydes, Ketones and Carboxylic Acids 9 Amines 10 Biomolecules

10 Biomolecules

10.1 Carbohydrates 10.2 Proteins 10.3 Enzymes 10.4 Vitamins 10.5 Nucleic Acids 10.6 Hormones

Nucleic Acids

NCERT Reference: Chapter 10 – Biomolecules – Page 277–279

Quick Notes

  • Two types of nucleic acid: DNA (deoxyribonucleic acid) and RNA (ribonucleic acid).
  • Composed of nucleotides: phosphate group, sugar (ribose or deoxyribose), and nitrogenous base.
  • DNA is double-stranded and stores genetic information.
  • RNA is single-stranded and involved in protein synthesis.
  • Nucleic acids are called polynucleotides due to repeated nucleotide units.

Full Notes

Nucleic acids are biomolecules responsible for the storage and transmission of genetic information. They control all cellular activities by coding for the synthesis of proteins.

Chemical Composition of Nucleic Acids

Nucleic acids are polymers of nucleotides, and each nucleotide consists of:

Chemistry NCERT Class 12 diagram showing nucleotide components including phosphate group, pentose sugar, and nitrogenous base for DNA and RNA.

A nucleotide = Nitrogen base + Sugar + Phosphate
A nucleoside = Nitrogen base + Sugar

The nucleotides are joined by phosphodiester bonds between 3′- and 5′- positions of adjacent sugar molecules.

Structure of DNA

DNA (Deoxyribonucleic Acid) is a polymer made of repeating nucleotide units.

Chemistry NCERT Class 12 image of DNA polynucleotide strand highlighting sugar-phosphate backbone and attached nitrogenous bases.

Nucleotides are linked by covalent bonds between the phosphate of one nucleotide and the deoxyribose of another.

These phosphodiester linkages occur between carbon atoms 5 and 3 on each pentose sugar. This forms a sugar-phosphate backbone with bases attached to the sugars.

DNA as a Double Helix

DNA consists of two complementary strands, forming a double helix.

Chemistry NCERT Class 12 diagram of the DNA double helix with antiparallel strands.

Hydrogen bonding occurs between specific base pairs on two strands of DNA.

Chemistry NCERT Class 12 figure showing complementary base pairing with A–T having two hydrogen bonds and C–G having three hydrogen bonds.

The specific base pairing occurs because of the hydrogen bonding that can form between paired bases. This is called complimentary base pairing.

RNA (Ribonucleic Acid)

Biological Functions of Nucleic Acids

Nucleic acids perform vital biological functions related to heredity and protein synthesis.

DNA

RNA

Summary