AQA biology a-level paper 2 questions and answers

AQA biology a-level paper 2 questions and answers describe and explain the steps in the light dependent reaction of photosynthesis - Correct Answer 1. photoionisation: light reaches chlorophyll in PSII, which is absorbed by an electron, which becomes excited and moves to a higher energy level. 2. the electron passes to a carrier protein in the thylakoid membrane, and is passed down a series of carrier molecules called an electron transfer chain. 3. as the electron moves down, energy is lost from the electron and is released as ATP. 4. the loss of electron from PSII is 'refilled' by an electron produced by photosynthesis, which also produces hydrogen and oxygen. 5. the lost electron reaches PSI, which absorbs light energy and boosts another electron to a higher energy level (excitation). 6. this electron also goes down an electron transport chain. 7. this reaches the final electron acceptor which is a proton. they combine to form H and reduce NADP to NADPH. describe and explain the steps in the light independent reaction pf photosynthesis. - Correct Answer 1. CO2 diffuses into stroma and combines with ribulose bisphosphate (RuBP) using the enzyme rubisco. 2. this forms an unstable 6 carbon molecule, which splits into 2 3 carbon molecules, glyercate-3-phosphate (G3P) . 3. G3P is reduced by NADPH to triose-phosphate (TP), which is aided by ATP for energy. 4. TP can be converted into useful organic substances. 5. TP can also be reformed into RuBP using ATP.