Deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) are made up of nucleic acids found in the nuclei of living cells. They are the vehicles of genetic inheritance.
Nucleic acids are condensation polymers of nucleotides. To understand their functions you will find it helpful to look at how their molecules are built up and the structures of these molecules.
The building blocks
Three types of chemicals make up the building blocks for nucleic acids.
Phosphates
These are based on the inorganic acid H3PO4 (phosphoric acid).
Two other acids may be formed from phosphoric acid by condensation reactions
Two important reactions of the hydroxyl groups in phosphoric acid are:
Sugars
The sugars in DNA and RNA are pentoses.
Organic bases
There are four organic bases involved in the formation of DNA molecules:
guanine(G)
thymine(T) T and C are single-ring pyrimidine bases.
cytosine(C)
In RNA the four bases are the same except for thymine which is replaced by uracil (U), a pyrimidine base.
Adenine, guanine, thymine, cytosine and uracil are bases because of the presence of one or more of the following groups: - NH2, - NH - and = N - groups. Importantly, - NH2 and - NH - groups can react with carboxylic acids and phosphoric acid to form amides.
Putting the building blocks together
In all nucleotide molecules the bonds holding the phosphate group to the sugar and the base to the sugar are both products of condensation reactions. Water is eliminated when they form. In both cases the oxygen to form the water has come from the sugar's -OH groups.
Nucleic acids are condensation polymers of nucleotides. To understand their functions you will find it helpful to look at how their molecules are built up and the structures of these molecules.
The building blocks
Three types of chemicals make up the building blocks for nucleic acids.
Phosphates
These are based on the inorganic acid H3PO4 (phosphoric acid).
Two other acids may be formed from phosphoric acid by condensation reactions
Two important reactions of the hydroxyl groups in phosphoric acid are:
- with alcohols to form ester groups
- with amines to form amide groups
Sugars
The sugars in DNA and RNA are pentoses.
- in DNA the sugar is deoxyribose
- in RNA the sugar is ribose
Organic bases
There are four organic bases involved in the formation of DNA molecules:
- adenine and guanine (both purines containing two rings in their structures)
- thymine and cytosine (both pyrimidines containing only one ring in their structures)
guanine(G)
thymine(T) T and C are single-ring pyrimidine bases.
cytosine(C)
In RNA the four bases are the same except for thymine which is replaced by uracil (U), a pyrimidine base.
Adenine, guanine, thymine, cytosine and uracil are bases because of the presence of one or more of the following groups: - NH2, - NH - and = N - groups. Importantly, - NH2 and - NH - groups can react with carboxylic acids and phosphoric acid to form amides.
Putting the building blocks together
In all nucleotide molecules the bonds holding the phosphate group to the sugar and the base to the sugar are both products of condensation reactions. Water is eliminated when they form. In both cases the oxygen to form the water has come from the sugar's -OH groups.