1) Structure Of Nucleic Acids

2) Functions Of Nucleic Acids

3) Structure Of Proteins

4) Functions Of Proteins

Introduction It refers to the Nucleic Acids Like DNA & RNA.

It is divided into 4 levels:

Primary

Secondary

Tertiary

Quaternary

Primary structure It is a linear sequence of nucleotides that are linked together by

Phosphodiester bonds.

It makes Primary structure of DNA or RNA.

Nucleotides consist of 3 components:

Nitrogenous base;

Adenine

Guanine

Cytosine

Thymine ( DNA only )

Uracil ( RNA only ) 5-carbon sugar which is called Deoxyribose (found in DNA)

and Ribose (found in RNA).

One or more phosphate groups.

The nitrogen bases Adenine and Guanine are Purine in structure .

Cytosine, Thymine and Uracil are Pyrimidine in Structure.

Secondary structure It is the set of interactions between bases.

In DNA double helix, the two strands of DNA are held together by H- Bonds.

It is responsible for the shape that the nucleic acid assumes.

Purines consist of a Double Ring Structure.

Pyrimidines has a Single Ringed Structure.

A Purine base always pairs with a pyrimidine base (Guanosine (G) pairs with

Cytosine(C) and Adenine(A) pairs with Thymine (T) or Uracil (U)).

DNA's secondary structure is predominantly determined by Base Pairing of the two

Polynucleotide Strands wrapped around each other to form a Double Helix.

In RNA, Secondary Structure consists of a Single Polynucleotide.

The Antiparallel Strands form a Helical Shape.

The 4 basic elements in the secondary structure of RNA are;

Helices

Loops

Bulges

Junctions.

Tertiary structure It is the locations of the atoms in 3D space.

Large-scale folding in a linear polymer occurs and the entire chain is folded into a specific 3D

shape.

There are 4 areas in which the structural forms of DNA can differ.

Handedness - right or left

Length of the helix turn

Number of base pairs per turn

Difference in size between the major and minor grooves

The tertiary arrangement of DNA's Double Helix in space includes;

B- DNA

A-DNA

Z-DNA

B-DNA is the most common form of DNA and it is a more narrow, elongated helix than A-DNA. Its

wide major groove makes it more accessible to proteins.

A-DNA is a form of the DNA duplex observed under dehydrating conditions. It is shorter and wider

than B-DNA. RNA adopts this double helical form, and RNA-DNA duplexes are mostly A-form.

Z-DNA is a relatively rare left-handed double-helix. Its function is unclear. It has a more narrow,

more elongated helix than A or B.

Quaternary structure It refers to a higher-level of organization of nucleic acids(interactions

of the nucleic acids with other molecules).

The most commonly seen form is Chromatin which leads to its

interactions with the Histone Proteins.

It is also refers to the interactions between separate RNA units in

Ribosome.

Functions of Nucleic Acids DNA: Transmission of Hereditary Characters.

Store house of genetic information control protein synthesis in cell.

Direct synthesis of RNA.

RNA: Direct synthesis of Specific Proteins.

m-RNA takes genetic message from RNA.

t-RNA transfers activated amino acid, to the site of protein synthesis.

r-RNA are mostly present in the ribosomes, and responsible for stability of m-RNA.

Introduction It is the 3D arrangement of atoms in a Protein Molecule.

Proteins are polypeptides made from sequences of monomer amino acids.

Proteins fold into one or more specific spatial conformations driven by a number of Non-Covalent interactions such as H-Bonding, Ionic Interactions, Van Der Waal Forces, and Hydrophobic packing.

Protein structures range in size from tens to several thousand amino acids.

A protein may undergo reversible structural changes in performing its biological function.

The alternative structures of the same protein are referred to as different conformations.

Primary Structure It refers to the linear sequence of

amino acids in the polypeptide chain.

It is held together by Covalent Bonds

like Peptide Bonds.

The 2 ends of the Polypeptide Chain are referred to

as the Carboxyl Terminus (C-terminus) and the

Amino Terminus(N-terminus).

It is determined by the Gene corresponding to the

Protein.

Secondary Structure It refers to highly regular local sub-structures on the actual

polypeptide backbone chain.

There are 3 main types of Secondary Structures;

Alpha Helix

Triple Helix

Beta Pleated Sheet

The Alpha Helix is a right-handed coiled strand. The stability to the structure is given by H-bonding.

The Triple Helix is 3 polypeptide chains woven together. H -bonding between –OH groups gives a strong structure.

The Beta –Pleated Sheet is created by inter-strand H-Bonding. It is more stable due to the well-aligned hydrogen bonds.

Tertiary Structure It is the overall 3D shape of an entire protein

molecule.

The alpha-helixes and beta pleated-sheets are folded into a compact Globular Structure.

There are; Disulphide Bonds - A strong double bond (S=S) is formed

between the Sulphur atoms within the Cysteine monomers.

Ionic Bonds - If 2 oppositely charged 'R' groups (+ve and -ve) are found close to each other, and ionic bond forms between them.

Hydrogen Bonds - Typical H-bonds.

Hydrophobic and Hydrophilic Interactions - Some amino acids may be hydrophobic while others are hydrophilic.

Quaternary Structure It is the Complete 3-D structure of a protein with

multiple peptides or proteins.

It is stabilized by a variety of bonding interactions

including H-bonding, Salt bridges, and Disulfide

bonds which holds the various chains into a

particular geometry.

Functions Of Proteins Repair and Maintenance - Protein is termed the building block of the body.

Energy - Protein is a major source of energy.

Antibodies - They are specialized proteins involved in defending the body

from antigens (foreign invaders).

Contractile Proteins - They are responsible for movement. Examples

include actin and myosin.

Enzymes -They are proteins that facilitate biochemical reactions. They are

often referred to as catalysts because they speed up chemical reactions.

Hormonal Proteins - They are messenger proteins which help to

coordinate certain bodily activities. Examples include insulin, oxytocin etc.

Structural Proteins - They are fibrous and stringy and provide support.

Examples include keratin, collagen, and elastin.

Storage Proteins - It Store Amino Acids. Examples include casein, ferritin.

Transport Proteins - They are carrier proteins which move molecules from

one place to another around the body. Examples include hemoglobin and

Cytochromes.

Summary Nucleic Acid structure refers to the Nucleic Acids Like DNA & RNA.

It is divided into 4 levels.

Nucleic Acids Useful in Transmission of hereditary Characters, Direct

synthesis of specific proteins etc.

Protein Structure is the 3D arrangement of atoms in a Protein

Molecule.

It is divided into 4 Structures.

It has H-Bonding, Ionic Interactions, Van Der Waal Forces etc.

Proteins Helps for Repair and Maintenance, Energy etc.

References Websites

healthyeating.sfgate.com

biology.about.com

nutristrategy.com

sophia.org

Journals

Proteins: Structure, Function, and Bioinformatics(ISI Journal Citation Reports © Ranking: 2014: 37/73 (Biophysics); 148/290 (Biochemistry & Molecular Biology))

Nucleic Acids – Chemistry and Applications (J. Org. Chem., 2013.Copyright © 2013 American Chemical Society)

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