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Alternative Pathways to Cellular Respiration!

Alternative Pathways to Cellular Respiration!. By: Julia Sigman, Izzie Gall, Kalah Haley, Valencia Watson. C4 Pathway. C4 stands for 4 carbon In order for the Calvin Cycle to take place, Rubisco must carry carbon dioxide to a 5 carbon molecule (Ribulose bisphosphate) during carbon fixation.

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Alternative Pathways to Cellular Respiration!

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  1. Alternative Pathways to Cellular Respiration! By: Julia Sigman, Izzie Gall, Kalah Haley, Valencia Watson

  2. C4 Pathway • C4 stands for 4 carbon • In order for the Calvin Cycle to take place, Rubisco must carry carbon dioxide to a 5 carbon molecule (Ribulose bisphosphate) during carbon fixation

  3. OH NO! • When carbon dioxide levels are low, rubisco has a hard time finding the carbon dioxide and needs assistance • Without the carbon dioxide, the calvin cycle cannot occur • In such cases, CO2 goes through stoma and goes to the mesophyll cell

  4. So what do we do about it? • Once in the mesophyll cell, we find PEP carboxylase, a 3C molecule • The CO2 then comes in and forms a 4C molecule (oxaloacetate) • The molecule rearranges to make the CO2 able to be broken off easier. • From there, the CO2 breaks off and a 3C molecule (pyruvate) is left to go through the cycle again

  5. What the what? • Basically, without rubisco carrying the CO2 the calvin cycle cannot fuction thus photosynthesis cannot occur. • When CO2 levels are low and rubisco has trouble finding it the CO2 travels through the stomata into the mesophyll cell and PEP carboxylase finds it and gives the CO2 to rubisco • Once the rubsico has the CO2 it travels to the bundle-sheath cell, where it surrounds the vein, thus the calvin cycle can continue

  6. What could go wrong? • The problem with the C4 pathway is that it uses ATP in addition to the ATP used in the calvin cycle • When pyruvate is left after the CO2 breaks off the malate, it takes ATP to rearrange the pyruvate into PEP.

  7. Who would do this? • Organisms that perform the calvin cycle are corn and sugar cane.

  8. CAM Pathway • CAM stands for Crassulacean Acid Metabolism • The CAM pathway is specific for day and night • The CAM pathway is utilized by plants that close their stomata during the day in order to prevent evaporation of their water

  9. Sleepover!! • Plants close their stomata during the day • As in C4 plants, the CAM Pathway uses PEP Carboxylase to fix a carbon molecule to a 4 Carbon molecule forming oxaloacetate • The oxaloacetate is rearranged and converted into malate, which is stored in cell vacuoles overnight (aka there is a CO2 slumber party)

  10. Ba-BAM! • Because the plants close their stomata during the day the CO2 gets backed up in the plant • The CO2 is stored overnight in the malate • During the day, when the stoma are closed, CO2 is removed from the stored malate and enters the Calvin Cycle and photosynthesis can continue

  11. What are examples of CAM plants? • Pineapples and cacti • The problem with the CAM cycle is, like the C4 pathway, it uses additional ATP.

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