C1.3 Structure of DNAs & its Functions

Semester 1: Foundation of Basic Science
Case 1: Chemistry of Life
Obj 3: Structure of DNAs & its Functions

DNA Deoxyribonucleic Acid

• DNA STRUCTURE

= Long chain of nucleotide

Nucleotide - composed of

1. Phosphate Group (PO4)
2. 5C Sugar (Ribose - RNA  /  Deoxyribose - DNA)
3. Nitrogenous Base (Purine -2 ring(AG) /  Pyrimidine-1 ring(TCU)

Basic Structure Of Nucleotide

Difference between Ribose and Deoxyribose of 5C Sugar

Difference between Purine & Pyrimidine of Nitrogenous Base

Nucleoside - nucleotide without PO4

Difference between Nucleoside and Nucleotide

Primary Structure
-Double stranded Helix
-the 2 strands are anti-parallel
-always read 5' to 3'
-polymers linked 3' to 5' by phosphodiester bridges
-bonds between

• polymers (phosphate & sugar) - phosphodiester bridges
• sugar & base - (purine =B-N9-glycosidic bond  /  pyrimidine =B-N1-glycosidic bond)
• base & base - hydrogen bond

Phosphodiester Bond (Phosphate-Sugar)

Glycosidic Bond (Sugar-Base)

Hydrogen Bond (Base-Base)

A-T (2)  /  G-C (3)

Secondary Structure
-sugar-phosphate backbone outside
-Bases (hydrogen bonded) inside
-Base-pairing rule   { A-T (2)  /  G-C (3) }

• DNA FUNCTIONS

1. Storage information
2. Replication
3. Access of infomation for protein synthesis

Functions of Nucleic acids
-Carrying the genetic information through generation


Functions of Nucleotides

1. Nucleoside 5'-triphosphates are carriers of energy, energy stores
2. Forming a portion of several important coenzymes such as NAD+, NADP+, FAD and coenzyme A
3. activated intermediates in numerous biosynthetic reactions, as SAM in glycoprotein synthesis
4. Cyclic nucleotides are signal molecules (second messenger) and regulators of many aspects of cellular metabolism
5. ATP is central to energy metabolism
6. GTP drives protein synthesis
7. CTP drives lipid synthesis
8. UTP drives carbohydrate metabolism

ATP

GTP

CTP

UTP