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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)