Nucleic Acids – Structure, Types, and Functions | DNA and RNA Notes for Class 10 & 12

Learn about Nucleic Acids (DNA & RNA) – their structure, types, and functions. Comprehensive Biology notes for Class 11 and 12, covering differences between DNA and RNA, nucleotides, and base pairing.

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In this article, we will study Nucleic Acids — the molecules of life that store and transmit genetic information. Nucleic acids are complex biomolecules made up of nucleotides, and they exist in two main forms: DNA (Deoxyribonucleic Acid) and RNA (Ribonucleic Acid). Understanding their structure and function is essential for students of Class 11, 12, and MDCAT Chemistry and Biology.

🔸 1. Definition of Nucleic Acids

Nucleic acids are biological macromolecules that store and transfer genetic information in living organisms.

They control cell functions by directing protein synthesis.

🔸 2. Components of Nucleic Acids

Each nucleotide (basic unit of nucleic acid) consists of:

Nitrogenous base (A, T, G, C, U)
Pentose sugar (deoxyribose or ribose)
Phosphate group

🔸 3. Types of Nucleic Acids

Type	Full Form	Sugar	Bases	Function
DNA	Deoxyribonucleic Acid	Deoxyribose	A, T, G, C	Stores genetic information
RNA	Ribonucleic Acid	Ribose	A, U, G, C	Helps in protein synthesis

🔸 4. Structure of DNA

Discovered by Watson and Crick (1953)
Double helix structure made of two polynucleotide strands
Complementary base pairing:
- Adenine (A) pairs with Thymine (T) → 2 hydrogen bonds
- Guanine (G) pairs with Cytosine (C) → 3 hydrogen bonds

🔸 5. Structure of RNA

Single-stranded molecule
Contains ribose sugar instead of deoxyribose
Uracil (U) replaces Thymine (T)
Three main types:
- mRNA (Messenger RNA)
- tRNA (Transfer RNA)
- rRNA (Ribosomal RNA)