C4 and CAM Photosynthesis Flashcards Preview

AP Biology 2014 > C4 and CAM Photosynthesis > Flashcards

Flashcards in C4 and CAM Photosynthesis Deck (12):

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



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

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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




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



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