Exam 1 - Photosynthesis Carbon Reactions Flashcards
What are the three phases of the Calvin cycle?
- carbon fixation
- reduction
- regeneration of CO2 receptor, RuBP
What is the role of Rubisco?
to catalyze the RuBP + CO2 reaction
What are the problems with Rubisco?
- very slow enzyme
- not picky and will use either CO2 and O2 as a substrate
Why do C3 plants have their name?
in C3 plants, initial fixation of CO2 forms a 3 carbon compound (3-phosphoglycerate)
Where do the 3 carbon compounds (3-phosphoglycerates) go in the Calvin cycle?
- some are used to make the final product, glucose
- others are recycled and used to regenerate the substrate RuBP
What allows plants to pull water from the roots up to their leaves?
negative water potential
What are the problems with plants and dehydration?
on hot, dry days, plants will close their stomata to conserve H2O, which limits photosynthesis
-closed stomata will result in reduced CO2 access and O2 buildup
What happens in photorespiration?
Rubisco adds O2 instead of CO2 into the Calvin cycle, producing one 3 carbon compound and a toxic 2 carbon compound
Why is it a problem for O2 to build up?
O2 is highly reactive, and can become charged to form Reactive Oxygen Species (ROs)
How do C4 plants minimize the cost of photorspiration?
by incorporating CO2 into four-carbon compounds in mesophyll cells
Which enzyme is required for C4 plants to incorporate 4-carbon compounds?
PEP carboxylase
Why does PEP carboxylase work as an alternate carbon fixation enzyme?
-PEP carboxylase has a higher affinity for CO2 than Rubisco, and can fix CO2 even when concentrations are low
Which cells are four-carbon compounds exported to in C4 plants?
bundle-sheath cells
