Question

In yeast, ethanol is produced from glucose under anaerobic conditions. What is the maximum amount of ethanol (in millimoles) that could theoretically be produced under the following conditions? A cell-free yeast extract is placed in a solution that contains 2.50 × 10² mmol glucose, 0.35 mmol ADP, 0.35 mmol Pi, 0.70 mmol ATP, 0.20 mmol NAD⁺ , and 0.20 mmol NADH. It is kept under anaerobic conditions.

Under the same conditions, what is the theoretical minimum amount of glucose (in millimoles) required in the solution to form the maximum amount of ethanol?

Answer 1

First, write the equation

Glucose + 2ADP + 2Pi --> 2Ethanol + 2 ATP + CO2

then..

from the equation, ratio is

1:2:2 --> 2:2:1

so..

clearly glucose is in excess, the limiting

1 mmol of glucose = 2 mmol of ethanol

so...

250 mmol --> 500 mmol of ethanol

therefore, max amount of ethanol should be 500 mmol = 0.5 mol

b)

theoretial min. glucose for max amount of ethanol

minimum --> 0.15 mmol

then...

it must be 1:1 ratio

so

0.15 mmol of glucose is the correct answer