3/24 lecture Flashcards
What are the thylakoid reactions of photosynthesis?
rxns that harvest light energy and use it to make ATP (AKA light rxns)
What are the stroma reactions of photosynthesis?
rxns that use CO2 to make glucose (AKA dark rxns, light-independent rxns, calvin cycle)
What is photorespiration?
fixation of oxygen instead of CO2 in the stroma rxns; rubisco fixes 1 O2 per 4 CO2 fixed (generally limits crop yields)
How could photorespiration be a problem?
heat increases the oxygenase activity of Rubsico, while water deficit closes stomata making CO2 limiting
Why is photorespiration wasteful?
it produces one usable 3-carbon product and one toxic 2-carbon product (glycolate);
cell loses one fixed carbon, also spends ATP and NADH to recycle glycolate and transport intermediates
3 theories for the usefulness of photorespiration:
- N assimilation
- Preventing NADPH backup when CO2 is limiting
- Providing materials for other metabolic pathways
What could improve photorespiration? why?
bacterial salvage pathway; its more simple and does not require the peroxisome or mitochondria
what are mesophyll cells?
fix CO2 into a 4-carbon acid
What do bundle sheath cells do?
release CO2 from the acid, and then perform photosynthesis
Why does C4 photosynthesis require ATP?
to regenerate the 3 carbon acid and energy to transport all the intermediates
C4 P vs. C3 P
C4 is effective at concentrating CO2 in the bundle sheath cells, particularly when CO2 is limiting; reduces photorespiration by virtue or concentration
Why C4 plants more water efficient?
b/c they do not need to conduct as much CO2 to perform the same amount of photosynthesis
When is C3 favored?
at cooler temperatures
UNFINISHED
dsfd
