Photorespiration and C4 Photosynethesis

[osimsDDS]

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This process is siiiiick:

Photorespiration:
Rubisco has a high affinity for O2 as for CO2 so when the stomata open to allow CO2 to enter it also allows O2 to enter and Rubisco via the calvin cycle fixes O2 as well as CO2, therefore, O2 does not yield a high energy product such as a carbohydrate as CO2 does...

C4 Photosynthesis:
Plants have come to adapt this process in order to only use CO2 instead of O2. To do this the stomata open and CO2 comes into the mesophyll cell where PEP (phosphoenol pyruvate) carboxylase changes the CO2 to OAA (oxaloacetate) and then it changes to Malate and enters the bundle sheath cell via plasmodesmata...Here Malate breaks into CO2 and pyruvate. Pyruvate gets back into the mesophyll cell to regenerate the cycle while CO2 gets integrated with RuBP (Rubisco) in the calvin cycle...Bundle sheath cells rarely make contact with intercellular space oxygen is rarely reaches them so RuBP is safe from oxygen and can make the desirable high energy carbohydrate it wants to make...

Hope this is interesting and also fills in some gaps between C3 and C4 plants...as it did for me

 

[ak47]

This process is siiiiick:

Photorespiration:
Rubisco has a high affinity for O2 as for CO2 so when the stomata open to allow CO2 to enter it also allows O2 to enter and Rubisco via the calvin cycle fixes O2 as well as CO2, therefore, O2 does not yield a high energy product such as a carbohydrate as CO2 does...

C4 Photosynthesis:
Plants have come to adapt this process in order to only use CO2 instead of O2. To do this the stomata open and CO2 comes into the mesophyll cell where PEP (phosphoenol pyruvate) carboxylase changes the CO2 to OAA (oxaloacetate) and then it changes to Malate and enters the bundle sheath cell via plasmodesmata...Here Malate breaks into CO2 and pyruvate. Pyruvate gets back into the mesophyll cell to regenerate the cycle while CO2 gets integrated with RuBP (Rubisco) in the calvin cycle...Bundle sheath cells rarely make contact with intercellular space oxygen is rarely reaches them so RuBP is safe from oxygen and can make the desirable high energy carbohydrate it wants to make...

Hope this is interesting and also fills in some gaps between C3 and C4 plants...as it did for me

man, plants are so baller!!

 

[osimsDDS]

Another process called CAM photosynthesis:

This happens when the stomata during the night open and CO2 is let into the cells, PEP carboxylase produces OAA from CO2 and then OAA is made into Malic Acid and is stored in the vacuole of the cell (alot of Malic acid accumulates)...During the day when the stomata are closed Malic acid is released from the vacuole and transfered back into OAA and then into CO2 and PEP...then the CO2 binds to RuBP and calvin cycle continues...

AGAIN this is another adaptation to photorespiration which is not beneficial for plants...

A good point also in this process is that Malic acid is an ACID and therefore the plant cells gain a bit of acidity (meaning the pH decreases) during the night because of the accumulation of malic acid...during the day however the malic acid is broken into OAA and then CO2 so the pH is restored in the cell...