OCR AS Biology

Revision Notes

2.3.2 Phosphorylated Nucleotides

Structure of ATP & ADP

  • All organisms require a constant supply of energy to maintain their cells and stay alive
  • In all organisms this energy is required for:
    • Anabolic reactions (building larger molecules from smaller molecules)
    • Moving substances across the cell membrane or moving substances within the cell
  • In animals energy is also required for:
    • Muscle contraction – to coordinate movement at the whole-organism level
    • The conduction of nerve impulses
  • In all known forms of life, ATP from respiration is used to transfer energy in all energy-requiring processes in cells
    • This is why ATP is known as the universal energy currency
  • Adenosine Triphosphate (ATP) is a nucleotide
    • The monomers of DNA and RNA are also nucleotide

ATP

  • Adenosine triphosphate (ATP) is the energy-carrying molecule that provides the energy to drive many processes inside living cells
  • ATP is another type of nucleic acid and hence it is structurally very similar to the nucleotides that make up DNA and RNA
  • It is a phosphorylated nucleotide
  • Adenosine (a nucleoside) can be combined with one, two or three phosphate groups
    • One phosphate group = adenosine monophosphate (AMP)
    • Two phosphate groups = adenosine diphosphate (ADP)
    • Three phosphate groups = adenosine triphosphate (ATP)

Structure of ATP, downloadable AS & A Level Biology revision notes

The structure of AMP, ADP and ATP.

Exam Tip

Don’t worry – you are not expected to know the structural formulae for the nucleotides that make up AMP, ADP and ATP (as in the diagram above)! You just need to learn the different groups that they are made up of ( pentose sugars and nitrogenous bases and how many phosphate groups,).

Remember that adenine is a nitrogenous base whereas adenosine is a nucleoside (a base – adenine, attached to a pentose sugar).

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