Untitled Flashcards Set

Q: What are the main stages of photosynthesis?
A: 1. Light-dependent reactions (in the thylakoid membrane).
2. The Calvin Cycle (in the stroma).

Q: Where does photosynthesis occur in plants?
A: In the chloroplasts of plant cells.

Q: What is the role of chlorophyll in photosynthesis?
A: It absorbs light energy, primarily in the violet-blue and red parts of the spectrum, to drive the reactions.

Q: What is photolysis in photosynthesis?
A: The splitting of water molecules by light energy in Photosystem II, producing oxygen, protons, and electrons.

Q: What happens to the electrons released by photolysis?
A: They are passed to the electron transport chain in the thylakoid membrane.

Q: What is the primary product of Photosystem II?
A: ATP, synthesized via chemiosmosis.

Q: What is the primary product of Photosystem I?
A: NADPH, a high-energy electron carrier.

Q: What is the purpose of ATP and NADPH in photosynthesis?
A: They provide the energy and reducing power for the Calvin Cycle to synthesize sugars.

Q: How is the proton gradient created in the thylakoid membrane?
A: By the movement of electrons through the electron transport chain, pumping protons into the thylakoid lumen.

Q: What is chemiosmosis in photosynthesis?
A: The process of using a proton gradient to drive ATP synthesis via ATP synthase.

Q: What enzyme is responsible for ATP synthesis in the light reactions?
A: ATP synthase.

Q: What is the purpose of the Calvin Cycle?
A: To convert atmospheric CO₂ into organic sugars (G3P) using ATP and NADPH.

Q: What is carbon fixation, and which enzyme is responsible for it?
A: It’s the process of incorporating CO₂ into organic molecules, catalyzed by the enzyme RuBisCO.

Q: What is RuBisCO?
A: An enzyme that fixes CO₂ into RuBP during the first step of the Calvin Cycle.

Q: What molecule is regenerated at the end of the Calvin Cycle?
A: Ribulose-1,5-bisphosphate (RuBP).

Q: How many molecules of CO₂ are needed to produce one G3P in the Calvin Cycle?
A: Three molecules of CO₂.

Q: What are the three phases of the Calvin Cycle?
A: 1. Carbon fixation.
2. Reduction phase.
3. Regeneration of RuBP.

Q: What are the products of the Calvin Cycle?
A: G3P (used to form glucose), ADP, and NADP⁺.

Q: What role do accessory pigments play in photosynthesis?
A: They broaden the range of light wavelengths absorbed and protect chlorophyll from damage by excessive light.

Q: Why is the thylakoid membrane important?
A: It houses the photosystems, electron transport chain, and ATP synthase, all necessary for the light-dependent reactions.

Q: What is cyclic electron flow?
A: A pathway that produces ATP but not NADPH, recycling electrons back to Photosystem I.

Q: Why is oxygen produced during photosynthesis?
A: As a byproduct of water splitting in Photosystem II.

Q: What is the role of the stroma in photosynthesis?
A: It is the site of the Calvin Cycle where sugar synthesis occurs.

Q: What happens when chlorophyll absorbs light?
A: An electron is excited to a higher energy state.

Q: What is the source of energy that drives the Calvin Cycle?
A: ATP and NADPH produced in the light reactions.

Q: What wavelength of light does Photosystem II absorb best?
A: 680 nm (P680).

Q: What wavelength of light does Photosystem I absorb best?
A: 700 nm (P700).

Q: What happens to G3P produced in the Calvin Cycle?
A: It can be used to form glucose and other organic compounds.

Q: Why is photosynthesis considered a redox process?
A: Water is oxidized to oxygen, and carbon dioxide is reduced to form sugars.

Q: How does CO₂ enter the chloroplasts?
A: Through stomata, small openings in the leaf.

Q: What are carotenoids, and why are they important?
A: Accessory pigments that protect the chloroplast by dissipating excessive light energy as heat.

Q: Why do plants appear green?
A: Chlorophyll reflects green light and absorbs other wavelengths.

Q: What is the difference between the light-dependent reactions and the Calvin Cycle?
A: Light-dependent reactions produce energy (ATP and NADPH), while the Calvin Cycle uses that energy to synthesize sugars.

Q: What is photorespiration, and why is it inefficient?
A: A process where RuBisCO binds O₂ instead of CO₂, consuming energy without producing sugar.

Q: How do C4 plants minimize photorespiration?
A: By spatially separating carbon fixation and the Calvin Cycle in different cell types.

Q: How do CAM plants adapt to arid environments?
A: By fixing CO₂ at night and storing it as malate, then using it during the day for photosynthesis.

Q: What are the reactants of the light-dependent reactions?
A: Light, water, ADP, and NADP⁺.

Q: What are the products of the light-dependent reactions?
A: ATP, NADPH, and oxygen.

Q: Why is the splitting of water necessary in photosynthesis?
A: To provide electrons for the electron transport chain and protons for the proton gradient.

Q: What is the Z-scheme in photosynthesis?
A: A model describing the flow of electrons from water to NADP⁺ through Photosystem II and Photosystem I.

Q: What happens to NADPH in the Calvin Cycle?
A: It donates high-energy electrons to reduce 3-PGA into G3P.

Q: How many turns of the Calvin Cycle are required to produce one glucose molecule?
A: Six turns (producing two G3P molecules).

Q: What happens to the ADP and NADP⁺ after the Calvin Cycle?
A: They are recycled back to the light-dependent reactions.

Q: What is the role of plastoquinone (PQ) in the electron transport chain?
A: It transfers electrons from Photosystem II to the cytochrome complex.

Q: What is the cytochrome complex?
A: A protein that transfers electrons and pumps protons into the thylakoid lumen.

Q: What is plastocyanin (PC), and what does it do?
A: A mobile protein that transfers electrons from the cytochrome complex to Photosystem I.

Q: What happens to the oxygen generated during photosynthesis?
A: It is released into the atmosphere as a byproduct.

Q: How do ATP and NADPH interact in the Calvin Cycle?
A: ATP provides energy, and NADPH provides reducing power to convert 3-PGA to G3P.