Bio 221 Fall 2007
1. Make a sketch of bacterial “Central Metabolism,” including glycolysis, pyruvate oxidation and the TCA Cycle. Then add in the respiratory chain and oxidative phosphorylation.
A. Instead of the standard order of glycolytic reactions, Bacterium A first oxidizes glucose, and then hydrolyzes it (reversing these two steps compared to other bacteria). Instead of producing two molecules of glyceraldehyde-3-phosphate (G-3-P) from glucose hydrolysis, this type of glycolysis produces one molecule of G-3-P and one molecule of Pyruvate. Show (in a different color, maybe) how this modification would alter the sketch you made earlier. How would it affect the ATP and reducing power produced by glycolysis?
B. Instead of the normal TCA Cycle, Bacterium B bypasses the two oxidative decarboxylation reactions by splitting the 6-carbon isocitrate into succinate and a 2-carbon intermediate (call it ‘X’), which is combined with another 2-carbon Acetyl~CoA to produce the 4-carbon malate. [You can look at the full diagram of the TCA Cycle on slide 16 of lecture 11 to see where isocitrate, succinate and malate fit into the TCA Cycle, since I’m not asking you to memorize them.] Show (maybe in another different color) how this modification would alter the sketch you made earlier. How will the amount of ATP and reducing power produced by Bacterium B compare to that produced by other bacteria?
C. Here is a depiction of a typical Bacterial ATP Synthase, as used in oxidative phosphorylation. Note the 12 segments (subunits) labeled ‘c’ in the diagram. To what part of the ATP Synthase do they belong? Instead of 12 ‘c’ subunits, Archaea have 8. What consequence does this have for the amount of ATP that can be generated for a given PMF? (Hint: figure out the number of H+ from the PMF that it “costs” to make one ATP in a typical Bacterium, versus in Archaea.)