Unit 3.1 - the importance of ATP

Chemiosmosis - the flow of protons down an electrochemical gradient through ATP synthesase, coupled with the synthesis of ATP from ADP and an inorganic phosphate ion. 

ATP is produced on the internal membranes of the mitochondria and chloroplasts, when protons flow down an electrochemical gradient through through the enzyme ATP synthesase located at the stalked particles. 

Electrons and protons derived from H atoms both take different pathways in the synthesis of ATP:

1. Electrons 

• They are transferred from a donor molecule to a recipient.
• They are transferred down a chain of electron acceptors via a series of redox reactions: one molecule is oxidised (loss of electrons) whilst the other is reduced (gains electrons).
• Oxidation makes energy available, which is used to pump protons across the membrane. 

2. Protons 

• The energy released in the electron transport chain is enough to transpor the protons across the membrane via proton pumps.
• They gain a greater concentration on one side of the membrane, generating a electrochemical gradient. This is a source of potential energy.
• The protons flow down tthe gradient, through ATP synthetase (located in stalked particles…