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Transcript of C4
C4, C3, and CAM
CAM (Crassulacean Acid Metabolism)
CAM is named after the plant family in which it was first found (Crassulaceae) and because the CO2 is stored in the form of an acid before use in photosynthesis.
CAM plants include many succulents such as cactuses and also some orchids and bromeliads.
CAM plants also developed because of photorespiration. Photorespiration is respiratory process in many higher plants by which they take up oxygen in the light and give out some carbon dioxide, contrary to the general pattern of photosynthesis.
Stomata open at night and are usually closed during the day. The CO2 is converted to an acid and stored during the night. During the day, the acid is broken down and the CO2 is released to RUBISCO for photosynthesis.
RUBISCO is an enzyme present in plant chloroplasts, involved in fixing atmospheric carbon dioxide during photosynthesis and in oxygenation of the resulting compound during photorespiration.
The difference between CAM and C4 is that CAM plants have only one cell, and they they open their stomata at night and close them during the day. The CO2 they take in at night is incorporated into 4 carbon compounds and is sent off to the Calvin cycle during the day to make glucose.
Adaptive characteristics: Better water use efficiency than C3 plants under arid conditions due to opening stomata at night when transpiration rates are lower.
Called C3 because the CO2 is first incorporated into a 3-carbon compound.
Stomata are open during the day.
Photosynthesis takes place throughout the leaf.
Most broadleaf plants are C3 plants
95% of earths plants are C3 excluding some grasses.
Goes through the Calvin cycle
They breathe in CO2 and release O2
They are not exposed to extremely hot conditions so they go through light and dark reactions normally.
C3 Plant Diagram
C4 plants have 2 separate cells, mesophyll cells and bundle sheath cells. C4 plants use this method to combat photorespiration, which is when the plants breakdown glucose to form CO2 instead building glucose from CO2 and releasing O2.
The CO2 enters the mesophyll cell, and PEP (phosphorescence) carboxylase binds the CO2 to PEP to produce a 4 carbon compound. PEP carboxylase has no affinity for O2, unlike rubisco, which is why it will bind with the CO2 instead of the O2 in the plant. So the 4 carbon compound (could be oxaloacetate, malate) is then transferred through plasmodesmata to the bundle sheath cells, where it is broken down to CO2 and pyruvate.
The CO2 enters the calvin cycle to produce glucose. The pyruvate is then sent back to the mesophyll cells and with the use of ATP is converted to back to PEP so that it can combinewith more CO2.