C4 and CAM Photosynthesis Flashcards
CAM Plant Photosynthesis
Only in arid conditions
Process when a plant takes up CO2 at night when stomata are open and incorporates it into a variety of organic acids
During the day, when the stomata are closed CO2 is released from the organic acids for use in the Calvin Cycle
C4 Plants
Plant in which the Calvin Cycle is preceded by reactions that incorporate CO2 into a four-carbon compound
PEP Carboxylase
An enzyme in the carboxylases responsible for the formation of the four-carbon compound oxaloacetate by catalyzing the binding of one molecule of carbon dioxide to the three-carbon compound phosphoenolpyruvate.
PEP carboxylase is vital in CAM and C4 plants during photosynthesis. It serves as the catalyst for the following chemical reaction:
PEP + CO2 → oxaloacetate + Pi
Photorespiration
A metabolic pathway that consumes oxygen and ATP, releases CO2, and decreases photosynthetic output
Generally occurs on hot, bright days when stomata close and the O2/CO2 ratio in the leaf increases, favoring the binding of O2 rather than CO2 by rubisco
For more watch:
https://www.youtube.com/watch?v=EQvTEFCANTM
Bundle Sheath Cells
A layer of cells in plant leaves and stems that forms a sheath surrounding the vascular bundles. In C4 plants the bundle sheath cells contain chloroplasts and are the site of the Calvin cycle. The initial fixation of carbon dioxide to form malic acid takes place in the palisade mesophyll cells, which in C4 plants form a circle around the bundle sheath.
C4 and CAM Compared
Both are two evolutionary solutions to the problem of maintaining photosysnthesis with stomata partially or completely closed on hot, dry days
Both involve:
1) Preliminary incorporation of CO2 into organic acids
2) Transfer of CO2 to the Calvin Cycle
Oxaloacetate
4-carbon compound
Important intermediate in the citric acid cycle and in the C4 and CAM pathways of carbon fixation in photosynthesis
Phosphoenolpyruvate (PEP)
3-Carbon phosphorylated compound that is an important intermediate in glycolysis and is a reactant in the initial carbon fixation step in C4 and CAM photosynthesis
Glyceraldehyde-3-Phosphate (G3P)
Phosphorylated 3-Carbon compound that is an important intermediate in glycolysis and in the Calvin Cycle; a 3-carbon carbohydrate that is the direct product of the Calvin Cycle; it is also an intermediate in glycolysis
Rubisco
The common name of ribulose biphosphate carboxylase/ oxygenase, the enzyme that catalyzes the fixation of CO2 in the carbon cycle
Ribulose Biphosphate (RuBP)
A five-carbon phosphorylated compound with a high energy potential that reacts with CO2 in the initial step of the carbon cycle
C3 Plants
Plant that carries out carbon fixation solely by the Calvin cycle; A plant that uses the Calvin Cycle for the initial steps that incorporate CO2 into organic material, forming a 3-carbon compound as the first stable intermediate
