VI.I. Photosynthesis Mechanism Flashcards
Q: What are the two main stages of photosynthesis?
light reactions
Calvin cycle (light-independent reactions)
Q: Where do the light reactions occur?
thylakoid membranes of the chloroplasts
What happens during the light reactions?
- Light energy is absorbed by chlorophyll, exciting electrons.
- Water molecules are split into oxygen, protons, and electrons (photolysis).
- The excited electrons pass through the electron transport chain (ETC).
- ATP and NADPH are produced as energy carriers.
role of photosystem II in the light reactions?
A: Photosystem II absorbs light, which excites electrons. These electrons are passed to the electron transport chain (ETC) after water is split to replenish the electrons, releasing oxygen as a byproduct.
role of photosystem I in the light reactions?
Photosystem I absorbs light to excite electrons again, which are then used to reduce NADP⁺ to NADPH.
Q: What happens in the electron transport chain (ETC) during the light reactions?
- Excited electrons move through a series of proteins.
- Their energy pumps protons into the thylakoid space, creating a proton gradient.
- This gradient powers ATP synthase to produce ATP via chemiosmosis.
Q: What is chemiosmosis in the light reactions?
the process by which the proton gradient created by the ETC drives the production of ATP as protons flow through ATP synthase.
Q: Where does the Calvin cycle occur?
stroma of the chloroplasts
three main phases of the Calvin cycle
Carbon fixation
Reduction
Regeneration of RuBP (ribulose bisphosphate)
Q: What happens during the carbon fixation phase of the Calvin cycle?
RuBP (ribulose bisphosphate) reacts with CO₂, catalyzed by the enzyme RuBisCO, forming an unstable 6-carbon compound that quickly splits into two 3-carbon molecules (3-PGA).
Q: What happens during the reduction phase of the Calvin cycle?
ATP and NADPH from the light reactions are used to convert 3-PGA into G3P (glyceraldehyde-3-phosphate), a 3-carbon sugar.
Some G3P molecules exit the cycle to be used for glucose synthesis.
Q: What happens during the regeneration of RuBP phase of the Calvin cycle?
G3P molecules are used to regenerate RuBP, allowing the cycle to continue. ATP is required for this process.
Q: How is glucose produced from the Calvin cycle?
A: Some of the G3P molecules produced in the Calvin cycle are used to form glucose and other carbohydrates.
Q: What are the main products of photosynthesis?
A: The main products of photosynthesis are glucose (C₆H₁₂O₆) and oxygen (O₂).
