Problem 2
Net Equation for Glycolysis and the Citric Acid Cycle Write the net biochemical equation for the metabolism of a molecule of glucose by glycolysis and the citric acid cycle, including all cofactors.
Problem 6
Pyruvate Dehydrogenase Cofactors and Mechanism Describe the role of each cofactor involved in the reaction catalyzed by the pyruvate dehydrogenase complex.
Problem 7
Thiamine Deficiency Individuals with a thiamine-deficient diet have relatively high levels of pyruvate in their blood. Explain this in biochemical terms.
Problem 8
Isocitrate Dehydrogenase Reaction What type of chemical reaction is involved in the conversion of isocitrate to \(a\) - ketoglutarate? Name and describe the role of any cofactors. What other reaction(s) of the citric acid cycle are of this same type?
Problem 12
Riboflavin Deficiency How would a riboflavin deficiency affect the functioning of the citric acid cycle? Explain your answer.
Problem 13
Oxaloacetate Pool What factors might decrease the pool of oxaloacetate available for the activity of the citric acid cycle? How can the pool of oxaloacetate be replenished?
Problem 14
Energy Yield from the Citric Acid Cycle The reaction catalyzed by succinyl-CoA synthetase produces the highenergy compound GTP. How is the free energy contained in GTP incorporated into the cellular ATP pool?
Problem 15
Respiration Studies in Isolated Mitochondria Cellular respiration can be studied in isolated mitochondria by measuring oxygen consumption under different conditions. If \(0.01 \mathrm{~m}\) sodium malonate is added to actively respiring mitochondria that are using pyruvate as fuel, respiration soon stops and a metabolic intermediate accumulates. a. What is the structure of this intermediate? b. Explain why it accumulates. c. Explain why oxygen consumption stops. d. Aside from removal of the malonate, what can overcome this inhibition of respiration? Explain.
Problem 16
Labeling Studies in Isolated Mitochondria Biochemists have often delineated the metabolic pathways of organic compounds by using a radioactively labeled substrate and following the fate of the label. a. How can you determine whether a suspension of isolated mitochondria metabolizes added glucose to \(\mathrm{CO}_{2}\) and \(\mathrm{H}_{2} \mathrm{O}\) ? b. Suppose you add a brief pulse of \(\left[3-{ }^{14} \mathrm{C}\right]\) pyruvate (labeled in the methyl position) to the mitochondria. After one turn of the citric acid cycle, what is the location of the \({ }^{14} \mathrm{C}\) in the oxaloacetate? Explain by tracing the \({ }^{14} \mathrm{C}\) label through the pathway. How many turns of the cycle are required to release all the \(\left[3-{ }^{14} \mathrm{C}\right]\) pyruvate as \(\mathrm{CO}_{2}\) ?
Problem 18
Role of the Vitamin Thiamine People with beriberi, a disease caused by thiamine deficiency, have elevated levels of blood pyruvate and \(a\)-ketoglutarate, especially after consuming a meal rich in glucose. How are these effects related to a deficiency of thiamine?
