Classification of nucleic acids
Nucleic acids are named because:
- found in nucleus of cells
- Later on discovered outside the nucleus
- DNA: Deoxyribonucleic Acid
- RNA: Ribonucleic Acid
Composition of nucleic acids
- Elemental composition: carbon, hydrogen, oxygen, nitrogen, phosphorous.
- Linear polymers of nucleotides (polynucleotides)
- Their building blocks are Nucleotides
Nucleotides are energy rich compounds that drive metabolic process in cell.
Nucleotide = nucleoside + phosphate
Each nucleotide consists of three compounds:
- Purine or Pyrimidine nucleobase (Nitrogenous base)
- Pentose sugar
- Phosphate group
Two types of nitrogenous bases: Purine and Pyrimidine Derivative
- Purine derivatives: Adenine and Guanine
- Pyrimidine derivative: Uracil, Thymine and Cytosine
This base is linked to sugar moiety by same carbon used in sugar-sugar bond.
Nucleosides: when ribose or 2-deoxyribose is combined with Purine or Pyrimidine base, Nucleoside is formed.
Nucleoside = pentose + bases
DNA：2-deoxyribose + A, T, C, G
RNA：ribose + A, U, C, G
linkage : sugar C1-pyrimidine N1 and sugar C1-purine N9
5-C keto sugar or pentose
One possess 2-deoxyribose and other contain d-ribose
Both sugar are present in Furanose form and beta-configuration
Pentose sugar form esters with phosphoric acid and is called Phosphodiester bond.
Molecular formula: H3PO4
Contains 3 monovalent hydroxyl group and a divalent oxygen atom
All linked to pentavalent phosphorous atom
Types of nucleic acids
- Deoxyribonucleic acid
- Double stranded
- Polymers of deoxyribonucleotides found in nucleus of the cell
- Function：Storing the Genetic Code
- Distribution：Eukaryote：nucleus (98%)，organelle (2%)；
- Ribonucleic acid
- Single stranded
- Polymers of ribonucleotides found in nucleus and cytoplasm of the cell
- Function: To transfer the genetic information from nucleus to cytoplasm for protein synthesis
- Distribution: cytoplasm (90%), nucleus (10%); virus
- Type： rRNA（ribosomal RNA）
other small RNA molecules
- messenger RNA
- carries genetic information from one or a few genes to a ribosome, where the corresponding proteins can be synthesized
- it is a complementary copy of selected regions of the DNA.
- It carries the genetic message from the nucleus to the cytoplasm and acts as the template for protein synthesis.
- Transfer RNA
- Also called Soluble RNA
- Modified bases
- Function：transfers a specific active amino acid to a growing polypeptide chain at the ribosome site of protein synthesis during translation
- There is at least one tRNA species for every amino acid (eg. tRNAAla )
- ribosome RNA
- Function：the central component of the ribosome, associated with protein synthesis.
- Some of them have catalytic and coenzyme function as well.
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