yeast saccharomyces cerevisiae

[raheela khan]

hello! my name is raheela and i am studying biology and psychology A-level.  
I have searched the internet for an investigation i am currently doing but 
need your help as i have tried and failed!  the investigation title is 'An 
investigation into the rate of fermentation by yeast' we were asked to 
investigate the rate of fermentation by yeast in the presence of different 
sugars i.e. Glucose sucrose maltose fructose and lactose. The rate of 
fermentation was measured by counting the number of Carbon dioxide bubbles 
produced for each sugar. my hypothesis stated that the rate of fermentation 
will be higher with sucrose(a disaccharide).  My results have supported this 
hypothsis as sucrose produced the highest number of bubbles then glucose 
then fructose but maltose and lactose did not produce any bubbles. The only 
thing i am finding difficult is an explation of the results in terms of 
glycolysis hence fermentation.  yeast Saccharomyces cerevisiae respires 
anaerobically to produce carbon dioxide alcohol and energy.  Glycolysis 
forms pyruvate molecules and the end result is 2ATP's being produce.  I 
think that sucrose being a disaccharide is broken down by enzyme invertase 
into glucose and fructose which are both used in glycolysis therfore there 
is a higher rate of fermentation by sucrose.  I would like someone to help 
me to find an explanation for my results and give me more info on my 
explanation.  please please can someone help me??????? if u can can you 
e-mail me!!! my address is baby_exodus at hotmail.com i need help urgently!!!
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