Archive for the ‘ Obj 3-DNA ’ Category

Obj 3-Structure of DNA & its Functions


= Deoxyribonucleic Acid

= 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

F05-01.jpg (1024×394)

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) }


  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