Photosynthesis Flashcards
How are photosynthesis and respiration related?
Photosynthesis converts CO2 and H2O into O2 and glucose.
Glucose is used as food by the plant and oxygen is a byproduct
Respiration converts O2 and glucose into H20 and CO2. ATP is the energy transformed in the process.
Describe the structure of a chloroplast
Double membrane
Thylakoids (flattened discs to form grana)
Intergranal lamellae (tubular extensions attach to thylakoids in adjacent grana)
Stroma (fluid filled matrix with high enzyme and substrate conc and loop of DNA)
Where do the light dependent and independent reactions occur?
Dependent- thylakoids
Independent- stroma
State the processes in the light dependent reaction
Photoionisation
Electron transport chain
Chemiosmosis
Photolysis of water
Reduction of NADP
Explain the role of light in photoionisation
Chlorophyll absorbs energy from light photons
Photosystem II excites 2 electrons causing them to be released from the chlorophyll
What happens in the ETC?
Electrons move down a series of carrier proteins embedded in the thylakoid membrane, undergo redox reactions, releasing energy
How does chemiosmosis produce ATP in the light dependent stage?
Some energy from the ETC is used to actively transport H+ ions down a conc gradient via ATP synthase
This catalyses ADP + Pi to ATP
Describe non cyclic photophosphorylation
Using photosystems I and II, electrons enter ETC to produce ATP.
NADP acts as final electron acceptor and is reduced.
Water is photolysed to release electrons to replace those lost in PSII
Purpose is to produced ATP and reduced NADP for the calvin cycle
Describe cyclic photophosphorylation
Uses only PSI.
No reduction of NADP and no water needed to replace lost electrons.
Electrons produce ATP and return directly to PSI
Purpose to produce ATP to meet surplus energy demand of cells.
Name the 3 main stages in the light independent reaction
Carbon fixation
Reduction
Regeneration
What happens during carbon fixation?
Reaction between CO2 and ribulosebiphosphate (RuBp), catalysed by ribulosebiphosphatecarboxylase (RuBisCo)
Forms an unstable 6C that breaks doen into two
glycerate phosphates
What happens during reduction?
2 GP are reduced to 2 triose phosphate (TP)
Requires NADP and 2 ATP
forms 2 NADP and ADP
Outline the roles of triose phosphate
Leaves the cycle to produce useful biological molecules
Involved in the regeneration of RuBP.
What is a limiting factor?
Determines the max rate of a reaction, even if other factors change to become more favorable
How does light intensity affect the rate of photosynthesis?
Less light = less ATP and NADPH produced o convert GP to TP in the light independent reaction
