Metabolic Flux Analysis

Some yeast cells growing on glucose can mix aerobic and anaerobic metabolism, that is, they consume oxygen and produce ethanol simultaneously when the O2 supply is restricted. The pathways for aerobic metabolism and ethanol production are both shown. A cell population consumes 10 mmole/l-hr of glucose. It also consumes 30 mmole/l-hr of O2(*Figure attached).

a. Calculate the ethanol production rate and CO2 production rate. List the reaction rates (mmol/l-hr) of the reactions a b, c, d, e.


These cells must maintain a constant total ATP production rate regardless of whether they grow aerobically or anaerobically. The ATP generation rate has been estimated to be 32 mmole per mole of glucose completely oxidized, with 2 mmoles of the ATP produced from the conversion of glucose to pyruvate. If the oxygen supply is shut down, answer the following questions.

b) We know that without O2 the TCA cycle (in mitochondria) cannot continue, why? Why can’t cells just break down pyruvate to CO2 if O2 is not involved in carbon catabolism in TCA cycle directly?

c) How much ethanol will be produced after the oxygen supply is shut down if the same ATP generation rate is to be sustained? What is the CO2 production rate?