Discuss the role of E286 in the proton transfer carried out by cytochrome c oxidase.  What are the D- and K-pathways? What is the fate of the protons from these two pathways? What is the role of E286?

Put these steps in the mechanism of chymotrypsin catalysis in order from first to last. Note that some references may not break out each of these steps individually, but all steps should be ordered. There will be eight steps.

Why does methotrexate prevent import of dihydrofolate reductase (DHFR) into mitochondria?

PLP can catalyze both \alpha, \beta elimination reactions and \beta, \gamma - elimination reactions. Propose a mechanism for the following PLP - catalyzed \beta, \gamma elimination

Why do the cytochrome electron-transfer processes have different standard reduction potentials, despite the fact that they all utilize the identical iron oxidation–reduction reaction?

Four electron carriers, a, b, c, and d, whose reduced and oxidized formscan be distinguished spectrophotometrically, are required for respirationin a bacterial electron transport system. In the presence of substrates andoxygen, three different inhibitors block respiration, yielding the patterns ofoxidation states shown below. What is the order of the carriers in the chainfrom substrates to O2, and where do the three inhibitors act?O and R indicate fully oxidized and fully reduced, respectively.

Activity of the light reactions (ETC) can be assayed using an artificial, reducible compound (e- acceptor) added to take the place of the terminal electron acceptor.  The artificial e- acceptor used is called DCPIP, a blue dye that turns colorless when it accepts electrons.  The reaction is: H2O + DCPIPoxidized (blue) --> O2 + DCPIPreduced (colorless) What molecule from the light reactions of photosynthesis does DCPIP compete with?

In the pathway for degradation of BCAAs, which reaction takes place prior to the action of the BCKDC and what is the essential coenzyme for the reaction?

What is the reduced product of complex IIII/cytochrome oxidase????

Propose structures for intermediates A and B in the scheme below. This three-step conversion is carried out by enzymes that require no redox cofactors (no FAD, NADH etc.) nor TPP. Which enzyme in the citric acid cycle has an activity most similar to enzyme 1? Which enzyme in the PPP or the citric acid cycle has an intermediate that bears similarity to intermediate B? H OH COO™ Enzl A Enz2 B Enz3 OH