Importance of ATP

• ATP is a nucleotide described as the 'universal energy currency'.
• ATP provides energy in all cells for all reactions.
• ATP releases energy in small, usable amounts.
• ATP is easily hydrolysed, removing the terminal phosphate group to release energy, forming ADP.
• The process of reattaching the 3 phosphate group with a high-energy bond is called phosphorylation, converting ADP back into ATP.
• ATP synthetase spans a membrane.
• The potential energy required to drive the enzyme to phosphorylate ADP comes from the flow of protons down an electrochemical gradient from one side of the membrane to the other by facilitated diffusion, this is chemiosmosis.
• High-energy electrons are delivered to the chain, powering a proton pump to pump the H+ ions through to the membrane-bound space (inter-membrane space or thylakoid space) from the matrix or stroma.
• Electron carrier molecules shuttle these electrons to the next proton pump in the chain, resulting in a build up of protons on one side of the membrane making an electrochemical gradient.
• Protons can only diffuse back to the matrix or stroma through ATP synthetase, releasing energy and used to synthesise ATP.
• In mitochondria, the proton pumps on the inner mitochondrial membrane are powered by high energy electrons from the hydrogen and pump protons into the intermembrane space where an electrochemical gradient is formed.
• Hydrogen atoms, from dehydrogenation reactions in glycolysis, the link reaction and Kreb's cycle, reduce coenzymes (NAD or FAD).
• The stalked particles are the ATP synthetase complexes.
• Oxygen is the final electron acceptor.
• Electrons are excited by photons of light and passed along an electron transport chain, powering proton pumps to pump protons across the membrane into the thylakoid space.
• In the matrix, these protons combine with the electrons from the chain and oxygen, forming water.
• There are some differences in the phosphorylation process between mitochondria and chloroplasts.
• Reduced coenzymes deliver hydrogen atoms to the electron transport chain in the inner mitochondrial membrane.
• The stalked particles are ATP synthetase and protons flow from inside the thylakoid back out into the stroma through this enzyme phosphorylating ADP to ATP.
• In both mitochondria and chloroplasts, the phosphorylation process generally involves an electron transport chain providing the energy for the creation of an electrochemical gradient that drives ATP synthetase to create ATP due to chemiosmosis.
• The thylakoid space is where the protons build up, forming an electrochemical gradient.
• The outer mitochondrial membrane is the site of the electron transport chain in the chloroplast.
• The thylakoid membrane is the site of the electron transport chain in the mitochondria.
• Protons flow from the inter-membrane space through these back into the matrix by chemiosmosis.
• The inner mitochondrial membrane is the location of the electron transport chain.
• Protons re-enter the stroma and combine with the electrons and NADP to form NADPH which will be used in the Calvin cycle.