Question

From your knowledge of glycolysis and the citric acid cycle, calculate the amount of ATP that can be produced from 20 molecules of lactose metabolized aerobically through glycolysis and the citric acid cycle.

Answer 1

Lactose is a disaccharide, made with Glucose and Galactose. It is cleaved by an enzyme called Lactase. After that glucose directly involved in Glycolysis and citric acid cycle followed by Electron Transport Chain and produce 32 ATPs. Similarly Galactose first converted into Glucose 6 phosphate and involved in Glycolysis, citric acid cycle and finally produce 32 ATPs like Glucose. Here 20 molecules of lactose produce 40 glucose equivalents (20 Glucose s & 20 Galactoses). Each one produce 32 ATPs. So total ATPs produced are: 40 x 32 = 1280