C4 photosynthesis Flashcards
What two structures does conversion of 2-phosphoglycolate into 3-phosphoglycerate occur
Peroxisome and mitochondria
What does conversion of 2-phosphoglycolate into 3-phosphoglycerate use (1) and produce (2)
Uses ATP and produces CO2 and NH3
What % yield does photrespirstion reduce from wheat and soybean
20%
36%
What is the trade off in different rubisco structures
Specifity vs rate of carboxylating
What is the effect of increased temperature on rubisco action
Increases rate of carboxylation but decreases specificity of rubisco for CO2 relative to O2
What 2 environmental conditions increase photorespiration
High temperatures and low water levels
Why do low water levels increase photorespiration
Stomata close to save water, photosynthesis continues and oxygen accumulates so more likely to combine with rubisco
Why do high temperatures increase photorespiration
Gases are less soluble in cytoplasm and stroma at high temperatures and oxygen stays in solution for longer
What are the 4 carbon concentrating mechanisms - CCMs
Dissolved inorganic pump
C2 photosynthesis
C4 photosynthesis
CAM
How does C2 increase CO2 around rubisco
Shuttles CO2 produced by photorespiration back to rubisco using glycine
How does C4 increase concentration of CO2 around rubisco to 3-10 times ambient level
Converts it into malate and shuttled to bundle sheath cells where rubisco is concentrated
How is CO2 converted and shuttled in C4 plants
CO2 —> HCo3 —> oxaloacetate —> malate
Moves into bundle sheath cell
Malate —> CO2
Moves into CBB cycle
Or ..
Malate converted into pyruvate then back to mesophyll cell
In what conditions to C3 plants perform photosynthesis better than C4 plants and where is the crossover point
Low temperatures and 25-30°C
Where does C4 abundance increase
High altitudes and close to equator
What are the two approaches in the attempted production of C4 rice
Genetic
and
Mutagenesis to introduce bundle sheath cells into rice
