Structure of Nucleotides (A-level Biology)

Structure of Nucleotides

Introduction to Nucleic Acids

DNA and RNA are both types of nucleic acids:

• DNA is responsible for storing genetic information. DNA is the key store of genetic information, which means all the instructions necessary for an organism to grow and to carry out necessary functions day to day.
• RNA is involved in the formation of proteins. RNA transfers the genetic information from DNA to help proteins form. RNA is structurally similar to DNA.

Structure of Nucleotides

• DNA and RNA are polymers made up of nucleotides. DNA and RNA contain many monomers called nucleotides, which make up the overall polymer. This is why we classify DNA and RNA as nucleic acids – because they are made up of nucleotides.
• Every nucleotide is made up of 3 components.
  • • A pentose sugar
    • A nitrogen containing organic base
    • A phosphate group.

Nitrogenous Bases

• Nitrogenous bases are organic, nitrogen containing chemical groups. There are two major classes of nitrogenous bases:

• • Purines – include adenine (A) and guanine (G). They have a double ring structure.
  • Pyrimidines – include thymine (T), cytosine (C) and uracil (U). They have a single ring structure

DNA and RNA nucleotides

It is important to understand the differences between DNA and RNA nucleotides. Carefully analyse both the table and diagrams.

Key differences:

1. RNA has a ribose sugar instead of a deoxyribose.
2. RNA has the base uracil instead of thymine.

Phosphorylated Nucleotides

When a nucleotide gets a phosphate group added to it, it becomes phosphorylated:

• ADP. Adenosine diphosphate (ADP) is a biological molecule consisting of the sugar ribose, the base adenine, and two phosphate groups.
• ATP: Adenosine triphosphate (ATP) is another biological molecule and is the energy currency of cells. It contains the same ribose sugar and base adenine as ADP, but contains three phosphate groups instead as suggested by its name.

We will cover ATP & ADP in more detail in later tutorials.