photosynthesis Flashcards
What is the overall chemical equation for photosynthesis?
6CO2 + 6H2O + lightenergy→C6H12O6 + 6O2
Where does the light-dependent reaction occur in the chloroplast?
In the thylakoid membrane
What are the main products of the light-dependent reactions?
ATP, NADPH, and oxygen (O₂)
What is the role of photosystem II in photosynthesis?
Photosystem II absorbs light energy to drive the splitting of water molecules (H2O) into oxygen, protons, and electrons
What is the primary function of the Calvin Cycle?
To convert carbon dioxide into glucose using ATP and NADPH produced in the light-dependent reactions
In which part of the chloroplast does the Calvin Cycle take place?
In the stroma
What enzyme is responsible for carbon fixation in the Calvin Cycle?
RuBisCO (Ribulose-1,5-bisphosphate carboxylase/oxygenase).
What are the three main phases of the Calvin Cycle?
- Carbon Fixation (CO₂ + RuBP → 3-PGA)
- Reduction (3-PGA → G3P using ATP and NADPH)
- Regeneration of RuBP (G3P → RuBP using ATP).
What is the Z-scheme in photosynthesis?
The Z-scheme describes the flow of electrons through photosystem II, the electron transport chain, and photosystem I, driven by light energy.
What is photorespiration, and why is it considered inefficient?
Photorespiration occurs when RuBisCO fixes oxygen instead of CO₂, leading to the production of a two-carbon compound that is recycled at an energy cost without producing sugars.
What adaptations do C4 plants have to minimize photorespiration?
C4 plants spatially separate carbon fixation and the Calvin Cycle, using PEP carboxylase to fix CO₂ in mesophyll cells, which is then transported to bundle-sheath cells for the Calvin Cycle.
What is CAM photosynthesis, and how does it differ from C4?
CAM plants temporally separate carbon fixation and the Calvin Cycle, fixing CO₂ at night and storing it as malate to be used during the day.
What is the role of plastoquinone in the light-dependent reactions?
Plastoquinone acts as a mobile electron carrier in the electron transport chain between photosystem II and the cytochrome b6f complex.
How does the proton gradient across the thylakoid membrane drive ATP synthesis?
The proton gradient powers ATP synthase, which phosphorylates ADP to ATP as protons flow back into the stroma through the enzyme.
How does non-cyclic photophosphorylation differ from cyclic photophosphorylation?
- Non-cyclic photophosphorylation involves both photosystems, produces ATP, NADPH, and O₂.
- Cyclic photophosphorylation only involves photosystem I and produces ATP without generating NADPH or O₂.
