1. Biochemistry of nucleotides & Nucleic Acids
By Dr. Howeida Abullah Mustafa
Lecture 1
Definition.
Function.
Biomedical importance.

2. Nucleotides
They are complex organic compounds found in all living organisms.
They are composed of :
A- a nitrogenous base
B- a sugar
C- phosphoric acid (phosphate).

3. Definition Nucleosides & nucleotides
Nucleoside = nitrogenous base + sugar.
When phosphate is added to a nucleoside it becomes a nucleotide.
Nucleotide = nucleoside + phosphate
Therefore a nucleotide can be defined as a phosphate ester of a nucleoside.
The nucleotides are precursors of nucleic acids.

4. Nucleotide Base PO4 Nucleoside Nucleotide = nucleoside + phosphate
Sugar

5. Definition Nucleic Acids
They are Polymers of four nucleotides
Linked by alternating sugar-phosphate bonds
They are:
A- Ribonucleic acid (RNA) (whose sugar is ribose)
B- Deoxyribonucleic acid (DNA) (whose sugar is deoxyribose).

6. Definition of Nucleoproteins
Macromolecular complex consisting of a protein linked to a nucleic acid, either DNA or RNA.
The proteins that combine with DNA are called histones and protamines.
The resulting nucleoproteins (deoxynucleoproteins) make up the chromosomes of living cells.
Many specific RNA nucleoproteins are also known; they have diverse cellular functions.
They are found greatly in Ribosomes.

7. Functions & Biomedical importance of nucleotides
Nucleotides are precursors of nucleic acids.
They are energy sources in various biochemical reactions e.g. ATP, c AMP, c GMP .
Some nucleotides are components of major coenzymes when linked to vitamins or vitamin derivatives.

8. Functions & Biomedical importance of nucleotides Cont.
They participate in protein synthesis,
They regulation enzyme activity, and
signal transduction.

9. Functions & Biomedical importance of nucleotides Cont.
Linked to sugars or lipids, nucleotides constitute key biosynthetic intermediates.
They participate in the biosynthesis of starch and glycogen.
Nucleoside-lipid derivatives are intermediates in lipid biosynthesis.

10. Functions & Biomedical importance of nucleotides Cont.
Medical applications:
Synthetic purine and pyrimidine (that contain halogens or additional nitrogen atoms) are used in chemotherapy of cancer and AIDS, (as they interfere with DNA Synthesis, therefore killing the rapidly dividing cells as in cases of tumor).
In case of viruses, they interfere with HIV replication.

11. Functions & Biomedical importance of nucleotides Cont.
Several nucleotides are used as immuno suppressors during organ transplantation, in order to avoid rejection of the transplanted organ by the host.
Purine analogues are used to treat gout.
(e.g. Allopurinol).

12. Biomedical importance of nucleic acids
Nucleic acids (DNA, RNA) are important information carrying molecules in all living organisms.
DNA
DNA serves 2 very important functions:
1- DNA transmits genetic information from one generation of cells to the next.
2- They provide information for the synthesis of protein.

13. Biomedical importance of nucleic acids Cont.
RNA
RNA is generally involved in the transfer of the genetic information stored in DNA through messenger RNA(mRNA) In a process called transcription.
And transfer of the genetic code into information used for protein synthesis, through transfer RNA (tRNA) (in a process called translation.