Unit 2 2.2 Cellular Respiration Higher Biology Unit 2 2.2 Cellular Respiration

Energy Release Respiration of glucose is a catabolic pathway. It occurs in the cells of all members of the three domains of life. It releases the energy stored in food. This energy is used to make the high energy molecule ATP.

Energy release ATP acts as the link between catabolic (energy releasing) reactions and anabolic (energy producing) reactions. e.g. from respiration to protein synthesis.

Energy release The function of ATP is to transfer chemical energy from catabolic to anabolic reactions.

Structure of ATP A molecule of adenosine triphosphate (ATP) is composed of adenosine and three inorganic phosphates (Pi). Adenosine Pi Pi Pi

Structure of ATP The energy held in ATP is released when the terminal bond is broken by the action of enzymes. Bond breaks Adenosine Pi Pi Pi E

Structure of ATP This results in the formation of adenosine diphosphate (ADP) and inorganic phosphate. Adenosine Pi Pi + Pi

Phosphorylation ATP can be regenerated from ADP and Pi in a reaction called phosphorylation. Phosphorylation is an enzyme-controlled reaction when phosphate is added to a molecule. Energy and the enzyme ATP synthase are required for phosphorylation. Energy stored ADP + Pi ATP Energy released

Phosphorylation The quantity of ATP in a cell at any given time should be fairly constant. This is because ATP is manufactured at the same time as it is used up. Therefore, there is no need for a living organism to possess a vast store of ATP. There is a rapid turnover of ATP in a cell.

Use of Energy Energy transferred by ATP from catabolic reactions is used for; Muscle contraction Protein synthesis Transmission of nerve impulses Active transport Cell division