A Level Biology: DNA Structure and Function

Introduction to DNA

Full Name: Deoxyribonucleic Acid (DNA)
Function: Codes for amino acid sequences, the primary structure of proteins
- Determines a protein's 3D shape and function
Importance: Essential in every cell, except red blood cells
Protection: DNA is the hard copy code for all proteins in a cell
Polymer Classification: DNA is a polymer in biological molecules

Polymer Name: Polynucleotide
Condensation Reaction:
- Joins nucleotides via removal of a water molecule
- Forms a phosphodiester bond (strong covalent bond)
Sugar-Phosphate Backbone:
- Strong structure due to covalent bonds
- Holds nucleotides together

Strands: Double-stranded polymer chains
Base Pairing: Complementary base pairs
- Cytosine (C) pairs with Guanine (G) via 3 hydrogen bonds
- Adenine (A) pairs with Thymine (T) via 2 hydrogen bonds
Hydrogen Bonds:
- Hold double strands together
- Allow DNA replication by enabling strand separation with minimal energy

Backbone Stability: Strong covalent phosphodiester bonds
Double Helix:
- Protects weaker hydrogen bonds inside
- Allows coiling and compacting of DNA
DNA Replication:
- Double-stranded nature allows each strand to serve as a template
Molecular Size:
- Large molecule capable of condensing around histones in eukaryotic cells
- Facilitates storage of large amounts of genetic information in a small space
Complementary Base Pairing:
- Ensures identical DNA copies during replication

DNA's structure and function are closely linked, providing stability and the ability to replicate and store genetic information effectively.

Recommended Videos:
- Proteins in A Level Biology
- Condensation Reactions
- DNA Replication

End of Lecture Notes