Answer to Question #187563 in Biochemistry for kafeja

Question #187563

Below is the concentration of lactic acid in the blood of an athlete before, immediately after and one hour after completing a 400 m sprint.

Before race 25 M Immediately after race 197 M One hour after race 26 M

How can you explain the large increase in lactic acid (25 M versus 197 M) at the completion of the race?

b) You have identified a mutant yeast whose glycolytic pathway is shorter due to the presence of a new enzyme catalysing the following reaction:

Glyceraldehyde-3-Phosphate + H2O + NAD+ →

3-phosphoglycerate + NADH + H+

What would the effect of this mutation have on this mutant yeast’s ability to grow under i) aerobic, and ii) anaerobic conditions?

Expert's answer

(a)As the athlete run or intensity of exercise increases, the blood lactate level starts to rise a state known as lactate threshold. This is because at lactate threshold, blood flow decreases and fast switch motor ability increases.


(I)The mutant yeast will be able to grow in aerobic conditions. This is because in

aerobic conditions of the mutant organism, the effect of the missing ATP-producing reaction is minimum as the energy in glucose is gathered in subsequent steps in glycolysis during its complete oxidation to CO2 along with H2O through the TCA cycle along with oxidative phosphorylation. ATP in aerobic conditions in place of the 30 ATP for the wild-type organism.


cells in yeast need energy for cellular processes. Since no net ATP is produced by the mutant organism under anaerobic conditions the mutant yeast will not be able to grow under this condition.

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