Biomolecules Nucleic Acids

Nucleic Acids

..and their structural foundations

Introduction:

• Nucleic acids are polynucleotides or long chainlike molecules composed of a series of nearly identical building blocks called nucleotides.
• The types: DNA (deoxyribonucleic acid) and RNA (ribonucleic acid)
• The structure of every protein, and ultimately of every biomolecule and cellular component, is a product of information programmed into the nucleotide sequence of a cell’s nucleic acids.

01

Nucleotides

Nucleotides:

• Nucleotides have three characteristic components:(1) a nitrogenous (nitrogen-containing) base, (2) a pentose, and (3) a phosphate.
• The molecule without the phosphate group is called a nucleoside.

Nitrogenous Bases:

• The nitrogenous bases are derivatives of two parent compounds, pyrimidine, and purine which are heterocyclic, aromatic compounds.

Phosphate group:

• Phosphate, chemical formula PO43-, is a chemical compound made up of one phosphorus and four oxygen atoms. When it is attached to a molecule containing carbon, it is called a phosphate group.
• Nucleotides at least contain one phosphate group.

Pentose Sugar:

• A Pentose is a five-carbon sugar.
• Nucleic acids have two kinds of pentoses. The recurring deoxyribonucleotide units of DNA contain 2'-deoxy-D-ribose, and the ribonucleotide units of RNA contain D-ribose.
• In nucleotides, both types of pentoses are in their beta-furanose (closed five-membered ring) form.

• they occur in one of a variety of conformations generally described as “puckered.”

Pentose Sugar:

02

The Bonds

Bonds Associated with the Bases:

• Adenine forms double hydrogen bonds with Thymine whereas Guanine forms triple hydrogen bonds with Cytosine.
• The base of a nucleotide is joined covalently (at N-1 of pyrimidines and N-9 of purines) in an N-Beta-glycosyl bond to the 1' carbon of the pentose.

Bonds Associated with Phosphate:

• The successive nucleotides are covalently linked through phosphate-group “bridges,”
• the 5'-phosphate group of one nucleotide unit is joined to the 3'-hydroxyl group of the next nucleotide- phosphodiester linkage.
• backbones of nucleic acids consist of alternating phosphate and pentose residues
• nitrogenous bases may be regarded as side groups joined to the backbone at regular intervals.

03

Deoxyribonucleic acids

3D model of DNA Structure:

• Two polynucleotide chains wound in a right-handed (clockwise) double-helix. Nucleotide chains are anti-parallel: 5’- 3’ and 3’-5’
• Sugar-phosphate backbones are on the outside of the double helix, and the bases are oriented towards the central axis.
• Complementary base pairs from opposite strands are bound together by weak hydrogen bonds.
• Base pairs are 0.34 nm apart. One complete turn of the helix requires 3.4 nm (10 bases/turn).
• Sugar-phosphate backbones are not equally-spaced, resulting in major and minor grooves

Forms of DNA:

04

Ribonucleic acids

The Structure of RNA:

• The diverse and often complex functions of RNAs reflect a diversity of structures much richer than that observed in DNA molecules.
• RNA assumes a right-handed helical conformation dominated by base stacking interactions which are stronger between two purines than between a purine and pyrimidine or between two pyrimidines
• Base pairing in RNA follows the pattern: G pairs with C, A pairs with U (or occasional T in some RNAs)

• Weak interactions, including base stacking, stabilize RNA structures.
• Weak interactions, including base stacking, stabilize RNA structures.

Types of RNA:

• There are many other types of RNA ( snRNA, scRNA etc.)
• rRNA- 75%
• tRNA- 10-15%
• mRNA- 5-10%

mRNA:

• mRNA is made from a DNA template during the process of transcription.
• It travels to ribosomes where protein synthesis takes place

rRNA:

• Ribosomes are a complex of proteins and rRNA

• The synthesis of proteins occurs in the ribosome

• The rRNA provides both structure and catalysis.

tRNA:

• Transports amino acids to the ribosomes where they are joined together to make proteins
• There is a specific tRNA for each aminoacid

• Recognition of the tRNA at the anti-codon communicates which amino acid is attached.

05

Differences

Thank You!

Presentation By:K.sri vinisha- AP22111260013