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Question #12 An actively respiring bacterial culture is supplied with pyruvate labeled on the methyl carbon with carbon-14 (carbon-14 is radioactive). Shortly after adding the label the citric acid intermediates are isolated and the position of the carbon-14 atom is determined. 12A Where is the carbon-14 label on alpha-ketoglutarate? Consider only the initial incorporation of carbon-14 in the first pass of labeled pyruvate through the citric acid cycle. [For full credit draw the relevant structures that show how pyruvate is transformed to alpha-ketoglutarate. No mechanisms are required, but provide balanced equations. You do not need to draw the structures of cofactors] 12B. What enzyme(s) in the pathway that convert pyruvate to alpha-ketoglutarate are regulated?