Plant Physiology and Photosynthesis Flashcards
7 cards from real USABO practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Plant Physiology and Photosynthesis flashcards as text
Which photosystem is responsible for the oxidation of water molecules during the light-dependent reactions of photosynthesis?
Answer: Photosystem II (P680)
Photosystem II (P680) catalyzes the light-driven oxidation of water, releasing O2, protons, and electrons that enter the electron transport chain.
What is the primary CO2 acceptor molecule in the Calvin cycle that is carboxylated by Rubisco?
Answer: Ribulose-1,5-bisphosphate (RuBP)
RuBP is the 5-carbon acceptor molecule that Rubisco carboxylates with CO2 to form two molecules of 3-PGA.
In C4 plants, which cell type performs initial CO2 fixation, and which enzyme catalyzes this reaction?
Answer: Mesophyll cells; PEP carboxylase
C4 plants use PEP carboxylase in mesophyll cells to fix CO2 into oxaloacetate, concentrating CO2 in bundle sheath cells to suppress photorespiration.
Which two products are generated by non-cyclic photophosphorylation (the Z-scheme) in photosynthesis?
Answer: ATP and NADPH
Non-cyclic photophosphorylation generates both ATP (via chemiosmosis) and NADPH (via NADP+ reduction at PSI), with water oxidized to release O2.
Photorespiration reduces photosynthetic efficiency primarily because it:
Answer: Releases previously fixed CO2 via the glycolate pathway
When Rubisco oxygenates RuBP, the products enter the glycolate pathway in peroxisomes and mitochondria, releasing CO2 and consuming ATP without net carbon gain.
Chlorophyll a and chlorophyll b absorb light most efficiently in which wavelength ranges?
Answer: Blue-violet (400-450 nm) and red (650-700 nm)
Chlorophylls absorb most strongly in the blue-violet (~430-450 nm) and red (~640-680 nm) regions and reflect green light, giving plants their color.
What drives ATP synthesis by ATP synthase (CF0-CF1) in the thylakoid membrane during photosynthesis?
Answer: A proton electrochemical gradient across the thylakoid membrane
Electron transport pumps H+ into the thylakoid lumen, creating a proton gradient that drives H+ back through CF0-CF1 ATP synthase, powering ATP synthesis via chemiosmosis.