3. ATP and energy release

ATP and Energy Release

Learning objectives: • Recognise the structure of ATP and ADP • Understand that ATP carries energy • Understand the role of ATP in metabolic pathways

ATP and energy release Adenosine triphosphate is the universal energy carrier and is required by all cells to release energy. It is composed of an adenine molecule and three inorganic phosphate molecules.

Energy is released when the end bond attaching the end phosphate is broken by an enzyme-controlled reaction into adenosine diphosphate (ADP) and a free inorganic phosphate molecule.

Adenosine

Pi

Pi

Pi

Adenosine

Pi

Pi

Pi

Adenosine diphosphate Energy is required to regenerate ATP from ADP and inorganic phosphate. This takes place in an enzyme -controlled reaction called phosphorylation.

When an energy-rich substance like glucose is broken down in a living cell, it releases energy which is used to produce ATP. This breakdown of glucose during cell respiration is a gradual process involving many enzyme controlled processes and this orderly release of energy is the ideal way for the chemical energy needed to regenerate ATP to be made available.

ATP is also regenerated and used during photosynthesis.

Since ATP can rapidly revert to ADP + Pi, it is able to make energy available for energy-requiring processes such as muscular contraction, active transport and transmission of nerve impulses.

Oxidation and Reduction Oxidation is the loss of hydrogen from a molecule, releasing energy.

Oxidation occurs in many metabolic pathways, e.g. respiration.

Reduction is the addition of hydrogen with the consumption of energy.

Reduction occurs during photosynthesis.

Hydrogen removed OXIDATION Energy released

Substrate reduced

Substrate oxidised

Hydrogen added REDUCTION Energy consumed

Oxidation Is Loss Reduction Is Gain

• Answer question 2 from Questions on page 19 of Torrance to form part of your notes