THE NUCLEIC ACIDS Mrs Manisha Sane PGT Chemistry KV VSN NAGPUR
Two types of nucleic acid are found • Deoxyribonucleic acid (DNA) • Ribonucleic acid (RNA)
The distribution of nucleic acids in the eukaryotic cell • DNA is found in the nucleus with small amounts in mitochondria and chloroplasts • RNA is found throughout the cell
NUCLEIC ACID STRUCTURE • Nucleic acids are polynucleotides • Their building blocks are nucleotides
PHOSPHATE SUGAR Ribose or Deoxyribose NUCLEOTIDE STRUCTURE NUCLEOTIDE
O C5 C1 C4 C3 C2 Ribose is a pentose sugar
DEOXYRIBOSE RIBOSE CH2OH CH2OH OH OH O O C C C C H H H H H H H H C C C C OH OH H OH Spot the difference
Nitrogenous Bases Pyrimidines Purines Adenine Thymine Cytosine Uracil Guanine In DNA In RNA
Purines & Pyrimidines in DNA Thymine Adenine Guanine Cytosine
P P P P P P THE SUGAR-PHOSPHATE BACKBONE • The nucleotides are all orientated in the same direction • The phosphate group joins the 3rd Carbon of one sugar to the 5th Carbon of the next in line.
G C C A T T P P P P P P ADDING IN THE BASES • The bases are attached to the 1st Carbon • Their order is important It determines the genetic information of the molecule
Hydrogen bonds C G T C T A P P P C P P G P P G P P T P A P A P DNA IS MADE OF TWO STRANDS OF POLYNUCLEOTIDE
DNA IS MADE OF TWO STRANDS OF POLYNUCLEOTIDE • The sister strands of the DNA molecule run in opposite directions (antiparallel) • They are joined by the bases • Each base is paired with a specific partner: A is always paired with T G is always paired with C Purine with Pyrimidine • Thus the sister strands are complementary but not identical • The bases are joined by hydrogen bonds, individually weak but collectively strong.
The Double Helix (1953) www.chem.ucsb.edu/.../images/WatsonCrick.jpg
Functions Of DNA • Replication • Transcription • Translation • Protein Synthesis Function Of RNA • It controls protein synthesis.
Biological Functions of Nucleic Acids:- • DNA is exclusively responsible for maintaining the identity of different species of organisms over millions of years. • DNA is the chemical basis of heredity and may be regarded as the reserve of genetic information. • A DNA molecule is capable of self duplication during cell division and identical DNA strands are transferred to daughter cells. • Another important function of nucleic acids is the protein synthesis in the cell. • Actually, the proteins are synthesised by various RNA molecules in the cell but the message for the synthesis of a particular protein is present in DNA.
Translation • Translation is the second process of protein biosynthesis (part of the overall process of gene expression).Translation occurs in the cytoplasm where the ribosomes are located. Ribosomes are made of a small and large subunit which surrounds the mRNA. In translation, messenger RNA (mRNA) is decoded to produce a specific polypeptide according to the rules specified by the genetic code. This is the process that converts an mRNA sequence into a chain of amino acids that form a protein
IMPORTANT TERMS • Codon---The Triplet of nucleotide coding a particular amino acid. Total 64,61 for inner amino acids and 3 for terminal amino acids. • Gene— Sequence of the nucleotides in DNA coding a particular protein. • Genetic code-- the relation between the nucleotide triplet and the amino acid. • Genetic code is Degenerate and more then one codons may code for same amino acids.
The Genetic Code Triplet code AUG start codon Encodes methionine UAA, UAG, UGA stop codons • The language of RNA to the language of protein: The genetic code is a triplet code in which three nucleotides in RNA specify one amino acid in protein. • RNA consists of four "letters": A, U, G, and C. Protein consists of 20 "letters": the amino acids.