32 - Wednesday Lecture 32 Final exam conflict for Monday...

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Wednesday, November 10, 2010 Lecture 32 . Final exam conflict for Monday 12/13 at 2PM? Meet immediately after lecture TODAY to choose date/time for make-up exam. This discussion has now happened. The make-up final exam will be on Wednesday 12/15 at 9:00AM, room TBA. In order to take this make-up exam, you must be on “the prof’s list” of eligible students (direct conflict with another final exam, or 2 other final exams within 24 hours of the regular Monday 2PM exam). If you are sick at the time of the regular exam, e-mail the prof! . Friday 11/12 at 2:55 – 4PM in Comstock B108: Interviews for the HCEC and for medical schools-- what are they looking for?! Monday’s lecture: . FA entry into mitochondrial matrix is regulated . cells control [CoA] in each membrane-bound compartment . β -oxidation of FA . "ketone bodies" as fuel for heart (and kidneys) . amino acid breakdown: transfer of amino group to alpha-KG, forming Glu Today's lecture: Page 223 In the liver mitochondrial matrix, bicarbonate combines with the phosphate of an ATP, then in a second step with an ammonium ion at the expense of another ATP to form carbamoyl phosphate. This can be called "Step 1" of the Urea Cycle (However, note that by definition of a cycle, the starting substrate reacts with the final product. For that reason, textbook authors usually “don’t count” the formation of carbamoyl phosphate as a step of the Urea Cycle!). The enzyme, carbamoyl phosphate synthetase , accounts for about 1/4 of the protein in the liver mitochondrial matrix! Wow that's a lot, considering all the other enzymes in the matrix (PDH, CAC). The overall reaction is a cycle-- the first reactant combines with the last product: . Carbamoyl phosphate, the first reactant, combines with ornithine, the last product, also in the matrix, to form citrulline and P i . . Citrulline is transported across the inner mitochondrial membrane. . Citrulline then combines with ATP and Asp in the third reaction to form argininosuccinate. This reaction and all the other reactions of the urea cycle occur "in the cytosol", but in fact, the enzymes for these reactions are all
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clustered together on the outer mitochondrial membrane. Note the Asp in this reaction. Soon we'll see where it came from. . Argininosuccinate in the cytosol reacts to form Arg plus fumarate in the fourth
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32 - Wednesday Lecture 32 Final exam conflict for Monday...

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