Hello there!
Thanks for joining me again.
Now that you have been introduced to the four
phased breakdown process of a glucose molecule,
in optimal conditions, let’s talk a little
bit more what happens if oxygen is not available
at the first stage (glycolysis).
As we remember, to really get the best value
for our ‘buck,’ in terms of extracting
the maximum amount of ATP from a single glucose
molecule, we needed to have oxygen available.
If this is the case, cellular respiration
takes place.
And, we just reviewed what happens in it.
However, if oxygen is not available fermentation
occurs.
During this process the pyruvate undergoes
reduction, and in total only two ATPs are
extracted from one glucose molecule.
This is rather inefficient, if you compare
it to the 38 APT molecules that can be extracted
under optimal conditions, is not it?
Now, depending on the type of organism there
is a little bit of a difference into what
this pyruvate is reduced into.
So, if we are talking about animals, something
called lactate gets produced.
Have you ever heard about a person exercising
intensely – and, by this I mean especially
aerobic exercise – where, they are working
so hard that there is just not going to be
enough of oxygen that they can take in to
meet the need of the body for oxygen.
Well, this is when you build up what we know
as lactic acid!
You remember, you can keep going, but eventually,
after you have stopped exercising, your muscles
will be so sore.
But, this is useful, because we can still
keep going even when not enough oxygen is
available, and – even more – the conversion
process of glucose to ATP is really fast.
Much faster than going through the full four
stages of the complete glucose breakdown.
So, there are times when this can be beneficial.
Really, the disadvantages are the losing out
on the maximum ATP amount that could be extracted,
and the fact that this process releases products
that are toxic to a cell.
So, we cannot be doing that forever – and,
there is a price to pay later on.
Remember, we get really sore after exercising,
and keeping exercising, beyond our oxygen
intake capacity.
Now, it does not have to be only animals that
rely on fermentation.
For example, yeast is used in a fermentation
reaction to produce alcohol from this pyruvate
that I mentioned earlier.
Can we think of examples where we use this
for food production?
Yes, there are many!
How about beer and wine?
Also, yoghurt!
And, of course, our pickles and sauerkraut.
As someone who lived in Germany I must advertise
that there is this great German restaurant
in Phoenix that really has the sauerkraut
thing figured out.
There are many health benefits that we could
discuss in relation to pickled food produce,
but let’s leave that until later.
So, your course textbook will offer more detail
about the fermentation process, but this is
where we will wrap it up for now with this
presentation!
Thanks for sticking around.
