week 4 handout

week 4 handout - Megan Lewis m3lewis@ucsd.edu OH: Thursday...

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Megan Lewis m3lewis@ucsd.edu OH: Thursday 1-2pm York 3010B Handout #4 PDH (pyruvate dehydrogenase) is needed for glycolysis to be connected to the TCA cycle. Without O2, the PDH rxn can’t occur and thus the maximum ATP that can then be made per glucose is 2ATP. Also know that pyruvate can only be broken down into 3CO2 (1 CO2 from PDH and 2 CO2 from TCA), ONLY in the mitochondria The PDH rxn is IRREVERSIBLE….once pyruvate is converted into Acetyl CoA you can’t back track and make glucose=Committed step Conversion of pyruvate to CO2=catabolism rxn (you are making CO2) Be able to recognize TPP’s structure and know that it is from Vitamin B1. (don’t worry about having to write it out…) KNOW how to write out the PDH rxn and know which enzyme goes with which step. PDH is an a-typical enzyme: it is allosterically inhibited by phosphorylation caused by PDkinase (thus PDH is shifted to its T state via the added phosphate bonds causing a conformational change in the enzyme that ends up reducing the enzymes affinity for pyruvate =>decreasing the amount of Acetyl CoA formed) Therefore, PD phosphorylase removes the Pi and shifts the PDH enzyme to its R state allowing for Acetyl CoA to be made from pyruvate. Note, that excess Pi = phosphorylation of the enzyme since you have excess Pi that need to be used. Therefore, ATP is an inhibitor of the enzyme (causing the enzyme to be inactive, ie in its T state so that Acetyl CoA can’t be made) Excess AMP on the other hand wants to soak up all of the Pi, therefore it removes the Pi from the PDH enzyme since it’s ‘greedy’. Therefore, excess AMP results in shifting the enzyme from its T to R state and thus activates the enzyme allowing for pyruvate to be turned into Acetyl CoA. Note that if you have excess AMP you want to make more ATP, and thus allow
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This note was uploaded on 06/02/2008 for the course BIBC BIBC 102 taught by Professor Price during the Spring '08 term at UCSD.

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week 4 handout - Megan Lewis m3lewis@ucsd.edu OH: Thursday...

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