Nucleic Acids

Role of nucleic acids in cells

A nucleic acid is composed of a long string of nucleotides A NUCLEOTIDE consists of a N containing base a 5C sugar (pentose) an inorganic phosphate group

nucleotide chemical structure

nucleotide simplified structure sugar base P P sugar base

There are 5 different bases: adenine, cytosine, guanine, thymine and uracil

Nucleotides join together by a condensation reaction An ester bond forms between the phosphate group of 1 nucleotide and the sugar group of another forming a polynucleotide

DNA DNA nucleotides are made up of 1 phosphate group 5C sugar deoxyribose 1 base of 4 thymine cytosine guanine adenine

DNA is a double helix It is made up of 2 strands joined together by H-bonds between the bases They join A-T & C-G

A forms 2 H bonds with T G forms 3 H bonds with C The specific pairing of bases is called complementary base pairing. There will always be the same number of complementary bases: A=T; G=C So the number of purines (A, G) will always be equal to the number of pyrimidines (C,T)

The strands are ANTI-PARALLEL This means the 2 strands run in opposite directions The sequence of bases makes up the genetic code

RNA RNA nucleotides are made up of 1 phosphate group 5C sugar Ribose 1 base of 4 uracil cytosine guanine adenine

RNA polynucleotides are single stranded There is no relationship between the number of purines and pyrimidines.

More detail to follow at A2!!! There are three main types of RNA mRNA messenger RNA formed in nucleus during transcription, carries genetic code into the cytoplasm rRNA ribosomal RNA Made in nucleolus , forms ribosomes, site of protein synthesis tRNA transfer RNA found in the cytoplasm, transports amino acids to the ribosomes during translation More detail to follow at A2!!!

Differences between DNA & RNA