B removal of coenzyme u from mitochondria results in

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Unformatted text preview: d out an elegant series of experiments using a sensitive pH meter to measure changes in hydrogen ion concentration in an anaerobic suspension of rat mitochondria. Explain each of the following observations: a) The anaerobic suspension was incubated with beta ­hydroxybutyrate, an oxidizable substrate. When a small amount of oxygen was then injected into the suspension, an immediate decrease in pH was observed followed by a gradual return to the original pH. b) When the first experiment was carried out in the presence of Triton X, a membrane ­disrupting detergent, no decrease in pH was observed when oxygen was injected into the suspension. c) The anaerobic suspension was incubated in the absence of an oxidizable substrate. When a small amount of ATP was injected into the suspension, an immediate decrease in pH was observed followed by a gradual return to the original pH. 29. The tabloids have announced a newly discovered compound called coenzyme U isolated from mitochondria. Several lines of evidence are presented in advancing the claim that coenzyme U is a previously unrecognized carrier in the electron ­ transport chain: a) When added to a mitochondrial suspension, coenzyme U is readily taken up by mitochondria. b) Removal of coenzyme U from mitochondria results in a decreased rate of oxygen consumption. c) Alternate oxidation and reduction of coenzyme U when it is bound to the mitochondrial membrane can be easily demonstrated. d) The rate of oxidation and reduction of coenzyme U in mitochondria is the same as the overall rate of electron transport. Which of these lines of evidence are the most (and least) convincing, and why? 4 Study guide Main points: Protein structure: Know structures of the amino acids and the approximate pKs of...
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