Question 2: (2 points) Z. mobilis is great at ethanol fermentation partly becaus

Question

Question 2: (2 points) Z. mobilis is great at ethanol fermentation partly because it blocks other commonly used pathways for glucose metabolism. The absence of what specific enzyme prevents Z. mobilis from undergoing glycolysis. Why is the absence of this specific enzyme a good (evolutionary) choice for blocking glycolysis? Question 3: (2 points) S. cerevisiae uses glycolysis-based fermentation to produce ethanol, while Z. mobilis uses the Entner-Doudoroff pathway. Give a reason for why more ethanol can be obtained per unit weight of Z. mobilis cells compared to unit weight of S. cerevisiae cells. Simply stating what is in the article is not sufficient. You need to explain your reasoning based on what is different between the ethanol producing pathways in the two organisms, and how that relates to cell mass. Question 4: (1 point) Name one enzyme you would introduce into Z. mobilis to decrease the flux through its ethanol-producing pathway.

Explanation / Answer

Answer 2):

Zymomonas mobilis uses the Entner–Doudoroff pathway (ED pathway) for glucose metabolism rather than Embden-Meyerhof-Parnas (EMP) pathway OR Glycolysis (which is more familier). The reason behind it is the Z. mobilis gene not encodes for an enzyme phosphofructokinase (which is crucial for glycolysis). Thus, prevent the bacteria from undergoing glycolysis.

The absence of phosphofructokinase enzyme from glucose metabolism pathway is the good (evolutionary) choice for blocking glycolysis because this enzyme is crucial for the glycolysis and in its absence the organism is compelled to use the Entner–Doudoroff pathway (ED pathway) for glucose metabolism. And the ED pathway is resulting to low ATP yeild as compared to glycolysis, thus, resulting to low cell mass and potential for higher ethanol yield.

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