11 - Photosynthesis Flashcards
What are the two stages of photosynthesis?
Light dependent
Light independent
Where does photosynthesis take place?
Chloroplasts
Describe what happens during photoionisation in the light-dependent reaction. (2)
Chlorophyll absorbs light
Light excites electrons in chlorophyll
Electrons lost
Chlorophyll becomes positively charged
What is the photolysis of water?
Light energy splits water to produce protons, electrons and oxygen.
Describe chemiosmotic theory.
Protons are actively transported from stroma into thylakoid using protein carriers (proton pumps) in the thylakoid membrane. The energy for this comes from photolysis of water.
High proton concentration inside thylakoid, low proton concentration in stroma.
Proteins move back out through ATP synthase which catalyses the formation of ATP from ADP and Pi by changing the channels shape.
What happens to protons after passing out of the thylakoid?
Taken up by NADP, to form reduced NADP. This is then used in the light-independent stage.
Where does the light-independent stage of photosynthesis occur?
Stroma of chloroplasts.
What does CO2 react with in the Calvin cycle? What is this catalysed by? What does this form? (3)
Ribulose bisphosphate, catalysed by rubisco. To form two molecules of glycerate-3-phosphate.
Name two products of the light-dependent reaction that are required for the light-independent reaction, and their roles with the light-independent. (3)
Reduced NADP
ATP
Used to reduce Glyerate-3-phosphate to Triose phosphate
(Reduced NADP goes to NADP, ATP goes to ADP + Pi)
What are the Triose phosphate products of the light-independent reaction used for? (2)
Regeneration of Ribulose bisphosphate
Conversion to useful organic substances ie cellulose, glucose.
What is needed to regenerate RuBP from Triose phosphate?
ATP, which breaks down to ADP and Pi, releasing energy.
