Built up from units called nucleotides.
Nucleotides are made up of three parts that are combined by condensation reactions.
- Phosphate ion – has same structure in all nucleotides
- Pentose sugar – in RNA it is ribose, in DNA it is deoxyribose
- Organic base which contains nitrogen
Five different types of bases divided into two groups
- Pyrimidine bases (single ring) – thymine, cytosine, uracil
- Purine bases (double ring) – adenine and guanine
DNA is always made up of 50% purines and 50% pyrimidines. There is always the same amount of thymine as adenine. Always the same amount of cytosine as guanine.
- Double stranded polymer of nucleotides or polynucleotide
- Polynucleotides may contain many million nucleotides
- Is a double helix – maintained by hydrogen bonding
- Pentose sugar is deoxyribose
- Contains adenine, guanine, cytosine, thymine
- Strands linked by pairs of organic bases
- Cytosine with guanine, adenine with thymine – link by H-bonds (complimentary base pairs)
Well suited to carry out its function because:
- It’s a very stable molecule, can pass from generation to…