Structure of Nucleic acids:
• The polynucleotide structure of nucleic acid is made
by esterification of phosphate radical of each
nucleotide to the hydroxyl group of C3 of the pentose
of the adjacent nucleotide.
Strucure of DNA
• DNA is present in the nucleus as part of
chromosomal structure which carries the genetic
• DNA if formed of 2 polynucleotide chains
twisted around each other in a double helix.
(dAMP, dGMP, dCMP and dTMP).
• Before division of the chromosomes, the
amount of DNA is doubled. The two strands of
DNA separate and upon each one strand the
compelemntary strand is synthesized.
• It consists of 75 to several thousands
ribonucleotides (AMP, GMP, CMP, UMP)
• Arranged in single strand
• Present mainly in the cytoplasm of the cell.
Types of RNA
Structure of RNA
1- Soluble or transfer RNA
• tRNA make up about 15% of the total
RNA in the cell.
• Present in the soluble phase of the
• Function: a carrier of amino acids from
the cytosol to the ribosome in the
process of protein synthesis
• It is a single strand made of 75-95 ribonucleotides.
• Shows extensive base pairing and acquires a clover
• It is twisted around itself in the middle part forming
2- Ribosomal RNA
• 80% of the cellular RNA
• Present in the ribosome of the cell.
complementary strand to the nucleolar DNA.
• It is broken into few pieces then associated
with several proteins to form ribosomal particles
• The ribosome is responsible for protein
synthesis from amino acids carried by the
proper tRNA according to the information
provided by mRNA.
3-Messenger RNA (mRNA):
• 5 % of RNA.
• It is synthesized in the nucleus from DNA
and then it passes to the ribosomes.
• Messenger RNA carries a message from
DNA in the nucleus to the ribosome in the
Adenine & Guanine Adenine & Guanine
Cytosine , Thymine Uracil, Cytosine
• Biological importance of nucleic acids
1-The genes which carry inherited characters are
2-The synthesis of proteins requires the 3 types
of RNA which are synthesized by DNA.
3- Trials are made to prove relationship between
cancer and nucleoprotein.
4- Viruses are rich in nucleoproteins
5- Memory may be related to the formation of
RNA in the brain.
• Free nucleotides play a role in energy
transfer, e.g. ADP, ATP, GDP, and GTP.
• Some coenzymes have nucleotide
structure such as FMN, FAD, and NAD.
• S-Adenosyl methionine (SAM) is a free
nucleoside which acts as methyl donor.
• 3`phosphoadenosine-5`phosphosulfate (PAPS) is a free
nucleotide which acts as sulfate
• cAMP, cGMP act as second
messenger for hormone action.
Adenosine monophosphate (AMP)
or Adenylic acid (AA).
(GMP) or Guanylic acid (GA)
Cytidine monophosphate (CMP)
or Cytidylic acid (CA)
Uridine monophosphate (UMP)
or Uridylic acid (UA)
Thymidine monophosphate (TMP)
or Thymidylic acid (TA)