glucose is phosphorolated into a phosphorolated hexose, which breaks down into two molecules of triosephosphate. the triosephosphate made from different sugars form different isomers of triosephosphate. e.g. you can have a triosephosphate which is a ketone or a aldehyde depending on the structure it has inhereted from the monosaccharde that was broken down.
the next stage is the oxidation stage. (it is important to note that aldehydes (e.g. glucose) can be oxidised into carboxylic acids more easily than can ketones ---> the carboxylic acid being pyruvate or pyruvic acid as some of you may have learnt. This process is carried out by the coenzyme NAD+.... which takes two hydrogens away from the triosephosphate to make 2NADH and 2pyruvate molecules, more easily when it be an aldehyde triosephosphate than a ketone triosephosphate.
the reason why aldehydes can be oxidised into carboxylic acid more easily than ketones is all due to the fact that aldehyde group allows for the easy removal of the hydrogen. but i dont think the examiners marking your coursework would want you to go that far.......
aldehydes, such as glucose can be oxidised into pyruvate more easily. pyruvate is turned into alcohol and carbon dioxides by the enzyme zymase.
this results in the continious falling of the concentration of the aldehyde (glucose) inside the cell because they are constantly oxidised into pyruvate ----> alcohol & CO2. Consequently a high a high concentration gradient accross the plasma membrane of the cell continually exists. soo a fast rate of active intake of this aldehyde occurs into cell.
ketones do not oxidise at all from what i have learned.... but i think we may come across a sugar that for example has an aldehyde isomer and a ketone isomer// i'm not sure!!! dont rely on that..
thats probably the reason why we get any fermentation at all with ketone sugars.
i havn't said much about the carrier proteins when talking about monosaccharides// only because cant see how the shape of the monosaccharide sugars can affect the efficiency of the protein carrier transporting it (especially when almost all of the structures are alike! except for fructose) // i think that the only reason why fructose is fermented faster than any disaccharide is because it is a monosaccharide.
a disaccharide is too large to be transported across through the protein carriers. disaccharides are broken down into monomers (monosaccharides) by special enzymes (hydrolysing enzymes) first to become small enough to be transported accross the plasma membrane..... and this takes time. therefore slower rate of fermentation
i havn't thought about differences between monosaccharides in detail. so i can't explain why a fructose would have a faster rate of fermenation than glucose or galactose if thats what you guys hav said.
sorry for the lecture// i get told by my teachers i have a habit of over complicating things. keep that in mind. dont write all of that if you are not needed to.... clarify it with ur teacher first. THE ABOVE WAS ALL MY OWN PERSONAL ASSUMPTION. I MAY BE WRONG!
let me know too/// coz i'm doing the same coursework in A2
i clarify too many things with my teachers... // they'v threatend to deduct marks if i askd for too many clarifications!!
i hope someone could return the favour.