Patients in shock experience decreased delivery of 02 to tissues, decreased activity of the pyruvate dehydrogenase complex, and increased anaerobic metabolism. Excess pyruvate is converted to lactate, which accumulates in tissues and in the blood, causing lactic acidosis. (a) Since 02 is not a reactant or product of the citric acid cycle, why do low levels of 02 decrease the activity of the pyruvate dehydrogenase complex? (b) To alleviate lactic acidosis, shock patients are sometimes given dichloroacetate, which inhibits pyruvate dehydrogenase kinase. How does this treatment affect the activity of the pyruvate dehydrogenase complex?