A comparison of the respiration of yeast in different sugar substrates.

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Biology Fermentation Practical

"A comparison of the respiration of yeast in different sugar substrates"

Aim: The aim was to compare the respiration of yeast in different substrates of sugars, i.e. between a monosaccharide (glucose) and a disaccharide (maltose)

Theory: There are three types of Carbohydrates, monosaccharides, disaccharides, and polysaccharides. The two, which I will be looking at, are, monosaccharide (glucose) and the disaccharide (maltose)

Classification and major properties of carbohydrates


Monosaccharides general formula:(CH20)n(n = 3 to 0)Small molecules with low molecular mass; sweet tasting; crystalline; readily soluble in water.Trioses, e.g. glyceraldehyde (C3H603)Hexoses e.g. glucose,
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Breaking this bond would slow the rate of CO2 produced in the respiration of yeast with the disaccharide in comparison to the monosaccharide.

My hypothesis can be justified by the way in which yeast digests with the chosen sugars.

"Yeast is a single-celled fungus, most in the class of Ascomycetes. The Ascomycetes yeasts include the common bread, beer, and wine-producing varieties of Saccharomyces Cereviseae." As yeast is a fungus and possesses no chlorophyll, it would be unable to photosynthesise. Therefore the yeast must obtain its carbohydrates by secreting enzymes onto the surface on which it is growing.

In the case of glucose and maltose, these enzymes are zymase and maltase. Maltose requires the specific maltase enzyme to first hydrolyse the glycosidic bond in between the glucose subunits of maltose before the zymase enzyme can break down the two á-glucose monomers from maltose. However glucose only requires the zymase enzyme to be broken down into ethanol and CO2, maltose. As the glycosidic bond needs to be hydrolysed in maltose to form two monomers of glucose, and additionally two enzymes are needed to break down maltose, is the reason why I think that the rate of CO2 produced by the respiration of yeast will be

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