Question

What product(s) is/are common to two of the reactions of the Citric Acid Cycle and the Pyruvate Dehydrogenase (the PDH) reaction?

		ATP, NADH, and CO2
		ATP and NADH
		ATP and CO2
		Both CO2 and NADH
		NADH only

Answer 1

Citric acid cycle reactions can be overall summarised as

Pyruvic acid + (4 NAD+) + (FAD+) +2 H2O +ADP > 3 CO2 + 4NADH + 4 (H+) + FADH2 +ATP

Reaction catalysed by pyruvate dehydrogenase can be represented as

Pyruvate + CoA + ( NAD+) > Acetyl CoA + CO2 + NADH + (H+)

Hence we can see common products in above reactions are both CO2 and NADH.

Reaction Catalysed by Pyruvale Dehydrogenase (PDH) Pyruvate formed as a result of glycolytic pathway occuring in cytosol, enters mitochondrial matrix to undergo decarboxylation by pyruvate dehydrogenase. The Ove sall reaction is presented as Pyruvate + COA INADE_PDH. 2+ → Acelyl CoA + CO2+ NADH+H s Citric acid cycle Pyruvate (30) Acetyl coAirco NADH+H* Oxaloacetic acid 40 NADA Mali 40 Citric acid (60) Ennst d-ketoglutarate (50) asco - NADH+H+ FADHZ . FADL . NADY? Succinic acid 40) - NADH+H+ ADD YATO Overall, citric acid cycle can be presented as below Pyruvic acid +4NADE + FADT + 2H,O+ADP 3.CO2 + 4 NADH +4H+ +FADH2 +ATP So, as seen above products common to two reactions are both CO₂ and NADH.