Hans Krebs used very thin slices of pigeon breast as part of his experimental sy

Question

Hans Krebs used very thin slices of pigeon breast as part of his experimental system to elucidate the cyclic pathway that bears his name. The thinly sliced pigeon breast is rich in mitochondria, and he found that he could measure the activity of the TCA cycle by monitoring the amount of oxygen consumed. (Why this is so will make more sense when we get to Ch. 14.) Krebs found that when he added 3 micromol of citric acid to his preparation, 36 micromol of oxygen were consumed, which was greater than would be expected if the citric acid was simply metabolized to CO2 and H2O? By what factor do you have to multiply the expected amount of oxygen consumed (on the basis of stoichiometry) to equal the actual amount of oxygen consumed? Enter your answer to the nearest tenth.

Explanation / Answer

Ans : The activity of the citric acid cycle can be monitored by monitoring the amount of O2 consumed. the greater the rate of O2 consumption, the faster the rate of the cycle.

The complete oxidation of citrate requires 4.5 mol of O2 for every mol of citrate.

C6H8O + 4.5 O2 ----------> 6CO2 +4H2O

Thus, 13.5 mol of O2 would be consumed by 3 mol of citrate.

So Citrate led to the consumption of far more O2 than can be accounted for simply by the oxidation of citrate itself. Citrate thus facilitated O2 consumption.

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