ATP

• Adenosine triphosphate is a phosphorylated nucleotide which is formed from a nitrogen containing organic base adenine, a 5 Carbon ribose sugar and a chain of 3 phosphate groups.
• The bonds between the phosphates in ATP require energy to form by a condensation reaction catalysed by the enzyme ATP synthase.
• Energy is released in small packets when the phosphate bonds in ATP are broken by the enzyme ATP hydrolase in a hydrolysis reaction.
• The phosphate bonds are relatively unstable which makes ATP a good energy source and poor long term energy store - ATP is the immediate energy source as the cell cannot get energy directly from glucose. 
• ATP is used in energy requiring processes in cells such as:

  • Phosphorylation of compounds
  • Active Transport
  • Metabolic Processes
  • Exocytosis
  • Movement
• Phosphorylation of compounds makes the compounds more reactive. Examples include phosphorylation of glucose to glucose phosphate in glycolysis, photophosphorylation in plant cells in photosynthesis.
• ATP provides the energy in active transport to change the shape of the carrier proteins in the plasma membrane to move molecules against a concentration gradient.
• ATP is used to provide the energy in metabolic processes, such as the synthesis of glycogen from glucose and polypeptides from amino acids.
• ATP is used for exocytosis- the secretion/ release of products from a cell.
• ATP is used for movement- muscle contraction, the movement of cilia.