Nucleoproteins

Nucleoproteins

Protein part

Protamine Histone

Nucleic acid

-DNA

-RNA

Nucleic Acids

-

Pentoses

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.

Types of nucleic acids

• Ribonucleic acids (RNA)

• Deoxyribonucleic acid (DNA)

Strucure of DNA• DNA is present in the nucleus as part of chromosomal

structure which carries the genetic information.

• DNA if formed of 2 polynucleotide chains twisted around each other in a double helix.

• It consists of deoxyribonucleotides (dAMP, dGMP, dCMP and dTMP).

Replication• 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.

RNA structure• 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

sRNA or tRNA rRNA mRNA

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 cytoplasm.

• 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

leaf appearance.• It is twisted around itself in the middle part forming

double helix.

2- Ribosomal RNA• 80% of the cellular RNA• Present in the ribosome of the cell.• Synthesized in the nucleolus as a complementary

strand to the nucleolar DNA.• It is broken into few pieces then associated

with several proteins to form ribosomal particles

(40S, 60S).

• 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 cytosol.

DNA RNA1-Sugar Deoxy ribose Ribose

2-Purines Adenine & Guanine Adenine & Guanine

3-Pyrimidines Cytosine , Thymine Uracil, Cytosine

4- Occurrence Nucleus Cytoplasm and nucleus

5-Double helical structure

present absent

6-Function Preservation of genetic characters

Protein synthesis

7-Types One type 3 types

• Biological importance of nucleic acids1-The genes which carry inherited characters are

DNA.

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

• 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 donor.

• cAMP, cGMP act as second messenger for hormone action.

BASES NUCLEOSIDES NUCLEOTIDES

Adenine Adenosine Adenosine monophosphate (AMP)

or Adenylic acid (AA).Guanine Guanosine Guanosine monophosphate

(GMP) or Guanylic acid (GA)

Cytosine Cytidine Cytidine monophosphate (CMP) or Cytidylic acid (CA)

Uracil Uridine Uridine monophosphate (UMP) or Uridylic acid (UA)

Thymine Thymidine Thymidine monophosphate (TMP) or Thymidylic acid (TA)