I have another question for you guys here.
It is said that during industrial prepartion of alcoholic
drinks, sugar or starch is converted into alcohol with
the help of enzyme. At this stage, the temperature is not
allowed to go aboove 21 deg cel or below 14 deg cel.
I understand the enzyme's role as catalyst. However why is it
that temperature is contained within a certain range? Is it because
the catalyst is functional at certain temperature ranges? (not sure
if my explanation is correct)
This is the reason why it is advantageous to have a teacher or
tuition teacher (eg. me!) with background in both Chemistry
and Biology. 
Strictly in terms of Chemistry, you would want temperature to be
as high as possible, as long as not exceeding the optimum
temperature for the enzyme (else the heat energy would overcome the
forces, particularly hydrogen bonds, that give the enzyme
a precise structural configuration required for the enzyme to
function; the enzyme would denature). This optimum temperature
range is different for every enzyme, but for the many (not
all!) enzymes studied under the 'O' and 'A' level syllabus, it
is usually close to 40 deg C.
Now, for this context of alcoholic (ethanolic) production by
enzymatic fermentation of carbohydrates, such as using the yeast
fungus, I will not give exact numerical values for optimum
temperature and such, because different sources, different
industrial companies, may use slightly different temperature
ranges.
But what I will highlight here, to contribute to your
understanding of this matter, is an important point that many
students, teachers, and textbooks neglect, and usually themselves
do not realize or understand.
It is this :
The reason why a seemingly low temperature (eg. 20+ deg C),
significantly lower than the optimum temperature for the yeast
enzymes involved (eg. 30+ deg C), is said to be the
'optimum temperature' for ethanol production via carbohydrate
fermentation, is because of biology - the enzymes may function
faster at a higher temperature, but the yeast fungus itself, does
not.
The optimum temperature for yeast to reproduce (you can't say
"have sex", since they reproduce asexually), is actually
significantly lower than the optimum temperature for
the enzymes within yeast that are involved in the fermentation
of alcohol to produce ethanol.
So it's a trade off. At lower temperatures, enzymes work slower,
but yeast reproduces faster, and hey, experimental evidence
indicates that (think about the exponential reproductive capability
of yeast fungus, akin to bacteria!) the trade off is well
worth it - you get a lot more ethanol produced if you lower the
temperature and make your yeast employees happy and busy
reproducing! More yeast = more ethanol produced!
Another example of how valuable it is to have background in
multiple disciplines (for myself, Chemistry and Biology), is how I
recall both the Biology teachers and the Chemistry teachers needed
my help to explain the following science mystery to students :
"Why is it that banana kept in the cold fridge ripens faster
than banana kept on the warm kitchen table?"
Well, ok, this riddle is actually a red herring, and not so much
about the advantages of being multidisciplinary. But
it's still a fun riddle nonetheless. Ask your friends in school to
solve this riddle!
