Maltose verses Glucose

[missgiggles]

Hello! im new to biologymad and ive looked on the search bit of the website but i cant really find anything that really explains the problems im having with my coursework.

Ive just finished the experiment but im really confussed about my results as they seem to contradict the expected results and i cant think of a reason why. IVe repeated it lots of times too to see if it was a one off but i get the same results. I would have thought that glucose would provide give the highest result as it is a monosaccaride and doesnt need to be hydrolysed, however maltose has prodcued about double the result glucose produced. They both both a similar shape curve as wellI was going to say something about moles as someone mentioned it on here but the solutions i used showed that maltose had exactly half the moles of glucose so i cant use that argument. I was also going to say thay yeast is used to using maltose as this is found in its natural environment, but it is composed of two glucoses so it should use glucose just as quick so i cant use that argument either I've looked everywhere but it all seems to suggest that glucose should have the highest resutls. I was just wondering if anyone knew why maltose produced the highest result, if there is a reason, or was it just my experiment going completly wrong and how can i justify my results if thats the case as i cant do any more practical work now!!

[Happydadtoo]

Hi!
If you read the posts here, you'll see that the hydrolysing step is of no importance - the rate limiting factor is the absorption of the sugar in the first place.

I'm surprised that you used maltose at half the molarity (good technique, but the standard method is to use equal w/v solutions (ie all 10% solutions))
If you DID do that, then the number of carbon atoms in the solutions should be the same and so the POTENTIAL CO2 production should be the same.

Any differences you observed are thus due to uptake - the respiration will be the same as the carbon available is the same.

Maltose and sucrose are both disaccharides and may well share the same carrier proteins through which they are absorbed through the memebrane; glucose is NOT noramlly found where the yeast lives, so it will need to synthesise new carrier proteins before it can utilise the carbon available.
See numerous previous posts about that and how you can redesign your expt to correct/allow for that point!!!

You don't, EVER need to JUSTIFY your results - just explain them - more maltose = more/quicker uptake of sugar = more/quicker CO2 producion in the short time you ran the expt.

Hope that helps a little
HD2

[missgiggles]

Ok thank you, i used a 5% solution for each sugar! I know now i should have used the same molarity!

So does yeast not have to hydrolyse the maltose initally? So could i theoretically say that maltose is found in the yeasts natural environment, therefore will have adapted to synthesise more maltose carrier protiens so therefore will produce more carbon dioxide in comparison to glucose as these carrier proteins wil take longer to synthesise?

Thank you so far for all your help - sorry to disturb you over the easter weekend! Have a good easter!

[Happydadtoo]

Ahhhhhhhhh.................!
NOW it begins to make sense!
5% solutions = 2x carbons in the maltose solution = more CO2 produced

RMM of maltose = 2x that of glucose, so, had you used Molarities, this would not be true and so the 2 solutions would have had the same POTENTIAL CO2 production - as it is, you had more carbon in the maltose soln, so more CO2 produced
As to the second point - probably not that much difference in rate of uptake (the hydrolysing step being v quick) as the maltose mihgt well use the same carrier proteins as sucrose.
AND!
When starch is hydrolysed by amylase (by yeast, as well as by anything else) the product is maltose
SO.....
Maltose carrier proteins therefore ARE on the surface of yeast (remember, it's breadmaking yeast you used!) whereas glucose Cps are probably NOT present

HD2 - just off to is mum, so no more replies for 4 days!

[missgiggles]

Thanks ever so much HD2 - you've cleared it all up for me now! Thanks for all your time!

Have a good Easter