fermentation

[wrahma1]

hi,
i recently conducted an experiment testing the effects of pH of three sugars (glucose, sucrose, lactose) on carbon dioxide production rates (i.e. rate of fermentation). the pH levels tested were 3, 7 and 11 respectively (for each sugar, therefore nine experiments were carried out). In all three sugars, the rate of carbon dioxide was highest at pH 7, lowest at pH 11. I am reallllly having difficulty explaining why that is. I know that the optimal pH of enzymes is from 6.5 to 7.5. He told us to explain this biologically, from perspective of enzyme catalyzed reaction and i seriously have no clue where to start explaining. ive been looking for info on this for hours. any help would be greatly appreciated!
thanks!

[MrMistery]

well, seems you already know the answer. the optimal pH for the activity of glycolysis enzymes is 7, and obviously it is not uniform. think of it as a curve, with the peak at 7, and which is more steep in the basic side than in the acidic side. the reason it evolved to tolerate a slight acidic pH better than a slight basic pH is probably because the organism itself produces some acid even when placed in pH 7, so it "evolved used to pH a little lower than 7". however, there is evolutionary reason why an enzyme active in a basic environment would be favorable in these conditions..
Hope it is clear now

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