0There are 4 crucial components in an organism.
1) Carbohydrate
2) Proteins
3) Fat
4) Nucleic Acids
In this lesson, the discussion will be on nucleic acids.
There are mainly two types of nucleic acids.
a) DNA ( de-oxy-ribonuceic acid)
b) RNA (ribonucleic acid)
DNA is a macromolecule which is the career of all the genetic information. DNA itself carries out all the main functions of the body in the molecular level.
Structure of DNA:
DNA basically is a polymer. It is a polymer of nucleotides. The nucleotide consists of 3 components.
•Nitrogen Base
• De oxy Ribose sugar (has 5 carbon atoms)
•Inorganic Phosphate
There are 4 types of nitrogen base in DNA.
•Adenine (A)
•Guanine (G)
•Thymine (T)
•Cytosine (C)
They are categorised into two sections. First one is Purine which consists of Adenine and Guanine. Another one is Pyrimidine which consists of Thymine and Cytosine.
DNA is a double-stranded helix. Each strand has the nucletonuc pairs. The pairing is made by bonding between the nitrogen bases between each stand.
Adenine always makes a pair with Thymine with double hydrogen bonds. Guanine makes a triple bond with Cytosine.
What is nucleotide?
= Nucleotide is a monomer consists of a nitrogen base, a de-oxy-ribose sugar and an inorganic phosphate residue. It is the basic constituent of a DNA molecule.
What is nucleoside?
= Nucleoside consists of a nitrogen base, a de-oxy-ribose sugar, but lacking a phosphate residue.
The bond between the nitrogen base and the sugar is called the glycosidic bond.
DNA has a helical structure. The two strands are in helix form but in a parallel manner. So there are loops in the helix (see figure below). Usually, DNA has a right-handed helix. There are 10 base pairs in a single loop.
The diameter of a DNA helix is 20 Å
The distance between two corresponding nucleotide pairs is 3.4 Å
So the length of a loop is 3.4x10= 34 Å.
