Lecture 31 - Lecture 31 1) Rubisco A large, slow enzyme...

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Lecture 31 1) Rubisco – A large, slow enzyme which bind both carbon dioxide and oxygen a) Very slow, very inefficient. Turnover is about 2 or 3 enzymes per second (other enzymes work about 1,000 to 25,000 per second) b) It is very non-specific, it even binds oxygen, and catalyses an OPPOSING reaction. (*See Slide). i) When oxygen is bound, both carbon dioxide and energy are drained from the system, can’t be used in the Calvin cycle. c) It limits the rate of primary production, plants have to make so much of it because of how slow it is. d) Rubisco has higher affinity for carbon dioxide, but there is more oxygen in the atmosphere. e) The importance of constraints – Rubisco didn’t evolve to favor carbon dioxide even more 2) Solutions a) Plants use C4 photosynthesis to separate co2 capture from o2 b) CAM – temporal segregation c) Both use Pep Carboxylase, which has a high specificity for co2 and doesn’t bind o2 3) Bundle sheath cells – form a sheath around the vascular tissue (veins). Carbon enters mesophyll cells and is fixed into a four carbon product (oxaloacetate) by pep-carboxylase. It costs ATP to convert pyruvate back into pep to start the cycle again. a)
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This note was uploaded on 02/09/2012 for the course BIOL 104 taught by Professor Smith during the Spring '09 term at Arkansas State.

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Lecture 31 - Lecture 31 1) Rubisco A large, slow enzyme...

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