Question

You are working out and you quickly feel your body temperature spike to a point that you are unable to continue to exercise. Identify the regulated step in glycolysis that has a direct impact on body temperature, explain why, what other effects occur if this step is not regulated, and ways to both activate and inhibit this enzyme.

Answer 1

Gluconeogenesis and glycolysis are coordinated so that within a cell one pathway is relatively inactive while the other is highly active. If both sets of reactions were highly active at the same time, the net result would be the hydrolysis of four nucleotide triphosphates (two ATP plus two GTP) per reaction cycle.

Both glycolysis and gluconeogenesis are highly exergonic(that's why there is increase in the body temperature ) under cellular conditions, and so there is no thermodynamic barrier to such simultaneous activity. However, the amounts and activities of the distinctive enzymes of each pathway are controlled so that both pathways are not highly active at the same time. The rate of glycolysis is also determined by the concentration of glucose, and the rate of gluconeogenesis by the concentrations of lactate and other precursors of glucose.

The interconversion of fructose 6-phosphate and fructose 1,6-bisphosphate is stringently controlled .( AMP stimulates phosphofructokinase, whereas ATP and citrate inhibit it) .

• Fructose 1,6-bisphosphatase, on the other hand, is inhibited by AMP and activated by citrate.

• A high level of AMP indicates that the energy charge is low and signals the need for ATP generation. Conversely, high levels of ATP and citrate indicate that the energy charge is high and that biosynthetic intermediates are abundant. Under these conditions, glycolysis is nearly switched off and gluconeogenesis is promoted.