How does a Sugar's Structure Affect Rate of Fermentation?

[Coraleen212]

Hey everyone, I'm a little confused over this issue. I recently conducted an experiment as part of my A2 coursework investigating the rates of fermentation produced by various sugars (glucose, fructose, galactose, maltose and lactose). I got the results and they fitted the pattern I expected ie. glucose giving the highest rate, then fructose etc. However, I need to use the structure of the sugar molecules to explain this difference in rate and this is where I'm stuck, as the structures of them seem to be fairly similiar (apart from the fact that some are monosaccharides and some are disaccharides). Can anyone help please? Much appreciated

[MrMistery]

Well, the disaccharides would have the slowest rate since they need to be turned into monosacharides first by hidrolysis.
Then i suppose your monosacharides had to be turned into glucose first, since glycolysis starts with glucose, not fructose, not galactose...

[Coraleen212]

Ahh, this was something I was confused about - fermentation can only occur with glucose? So all the other sugars would have to be converted to glucose before fermentation can take place, and other sugars cannot 'take glucose's place' in the reaction... is this correct?

[Coraleen212]

Anyone? Am I right on this or have I got the wrong end of the proverbial stick? XD

[kolean]

My first thought would be on the enzymes that are doing the fermentation, and what is their starting substrate (maybe it can be fructose and not glucose). Yeast (is this your fermentator?) can be complex in their substrates, depending on the species of yeast.

[JackBean]

Well, the disaccharides would have the slowest rate since they need to be turned into monosacharides first by hidrolysis.
Then i suppose your monosacharides had to be turned into glucose first, since glycolysis starts with glucose, not fructose, not galactose...

Not really, they are first phosphorylated by hexokinase, Fru can be then of course immediatelly used and other sugars are interconverted by cost of two ATPs

[sagaar]

Well, I too was wondering how the rate of fermentation could be influenced by the type or structure of the sugar. Since there are many types of sugar such as monosaccharaides and disaccharides, there could be definitely some kind of change in the rate of fermentation. I am so glad to see a rational explanation regarding this matter. I guess disaccharides seem to be slowest in this regard of rate of fermentation and glucose to be fastest since it is the first to go through glycolysis!

[bellyjelly]

sugar is food for yeast. And it encourages them to produce carbon dioxide.

So sugar would encourage the yeast ferment faster, thus producing more carbon dioxide.

[kyra13]

Speeds it up. Sugar is what powers the fermentation process