Light-dependent stage of photosynthesis 3.0 / 5 based on 1 rating ? BiologyCellular processesA2/A-levelWJEC Created by: sophiee96Created on: 12-08-13 10:44 The reactions of the light-dependent stage occur where? In the thylakoid membrane of the chloroplasts 1 of 29 What is the first stage? Photolysis 2 of 29 What does photolysis involve? The splitting of water molecules by light 3 of 29 What does the splitting of water by light produce? Hydrogen ions and electrons 4 of 29 What occurs after photolysis? The synthesis of ATP 5 of 29 What does the synthesis of ATP form? ADP and Pi 6 of 29 What is this type of phosphorylation known as? Photophosphorylation 7 of 29 Why? Because light energy is involved 8 of 29 What happens to the hydrogen ions? They combine with NADP to produce reduced NADP 9 of 29 What happens when light strikes a molecules at the reaction centre? An electron is raised to a higher energy level 10 of 29 What does this do? Sets up a flow of electrons 11 of 29 What is the electron flow known as? The 'Z-scheme' 12 of 29 What are the two ways ATP can be synthesised? Non-cyclic photophosphorylation and cyclic-photophosphorylation 13 of 29 Non-cyclic photophosphorylation involves which photosystems? Photosystem I and photosystem II 14 of 29 What happens first? Photons of light are absorbed by photosystem II 15 of 29 The photons of light are then passed to what? Chlorophyll a in the reaction centre 16 of 29 What does this cause? The displacement of two 'excited' electrons 17 of 29 What happens to the two high energy electrons? They are picked up by electron acceptors 18 of 29 What do these electron acceptors do? Pass the electrons along a chain of carriers through a proton pump and to photosystem I 19 of 29 What is the energy lost by the electrons used for? To convert ADP to ATP 20 of 29 What happens to photons of light that are absorbed by photosystem I? They are passed to chlorophyll a in the reaction centre 21 of 29 What does this cause? Two electrons to be emitted and raised to a higher energy level 22 of 29 What happens to these electrons? They are picked up by another electron acceptor 23 of 29 Photosystem II is not unstable, why? Because it has lost electrons 24 of 29 When are these replaced? When electrons become available from the splitting of water by photolysis 25 of 29 During photolysis a water molecule dissociates into what? Electrons, hydrogen ions and oxygen 26 of 29 The second electron acceptor (receives electrons from PS I) passes some of these electrons where? To hydrogen ions on the outside of the thylakoid membrane 27 of 29 What do the electrons do then? Reduce NADP 28 of 29 Why is this method of ATP production called non-cyclic photophosphorylation? Because these electrons are not recycled back into the chlorophyll 29 of 29
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