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so how do we use all of these different
calories especially the ones for basal
metabolic rate you need to know where
the majority of calories go to so a
quick graphic here to help us with that
first of all our brain uses almost 20%
again we have numbers on here you really
need to consider the relativity so which
organ uses the most calories all right
in our basal metabolic rate we consider
the liver which may be surprising but
the liver uses the majority of our
calories but it does an awful lot of
stuff it's always active it's always
working for us as well as our brain so
that also has a fairly high caloric
usage and then the heart is going to use
about 7 percent and the kidneys are
pretty active in using calories and then
skeletal muscle well of course we're
using the skeletal muscle to stand up
and move around at all times and so it
is going to use surprisingly just about
as much as the brain so the brain really
does have a high demand on our caloric
intake all the other organs fit into the
other slice of the pie so don't go
memorizing the numbers understand the
major users of our basal metabolic rate
the calories attributed to that brain
liver skeletal muscle heart and kidney
relative proportions are good enough
because again sources will vary on the
specific percentages so any calories
that we consume above and beyond our
basal metabolic needs pictured here are
going to be stored right and we
generally will store them as fat and
they can become an issue if we have an
imbalance in the intake and output of
those calories we need to consider for
your exam what calories come from you
are familiar with the major
macromolecules carbohydrate
proteins fats those are our sustenance
and then of course alcohol is an
additional consideration for us when
we're considering nutrition you can see
the USDA's recommendations of portion
sizes we moved from the pyramid to this
full plate concept with all the
different portions in various places
there are different arguments as to what
are the ideal proportions of proteins
carbohydrates and fats but for the
purposes of your exam the standard here
is probably going to be what they hit on
most heavily so keep these numbers in
mind for calories and for calories
sometimes you'll see carbohydrates noted
as 4.5 it seems for most sources 4 is
good enough alcohol 7 calories per gram
and fats having the most calories per
gram because it is an excellent calorie
storage spot so what you will also want
to do is recall where each of the
different fuels are utilized in cellular
respiration or metabolism and I'm
certain that you've spent plenty of time
examining those between anatomy and
physiology between cell and molecular
biology and in biochemistry for certain
you probably know many of the
intermediates along the pathway and what
you need to remember in the census of
nutrition is where each of these sources
enter into the respiratory cycle so is
it utilized in glycolysis is it utilized
in the Krebs cycle and where are the
intermediaries coming into there and
again that has been covered in the
cellular respiration lectures so keep
those pathways in mind the one that we
may have not spent as much time in is
alcohol metabolism alcohol metabolism is
a particularly hot topic in
a multidisciplinary area of nutrition
for the exams I think you've seen the
pathway before I want to alert you to
two key enzymes alcohol dehydrogenase
which is involved in conversion of
ethanol and some other alcohols to acid
aldehyde and then acid aldehyde
dehydrogenase taking more hydrogen's off
and the formation of acetate which can
easily enter into the Krebs or TCA cycle
so that it can be metabolized acetate is
harmless acid aldehyde on the other hand
is another story it turns out to be
fairly toxic a couple of drugs to
consider
there's firmeza pol or from hep is all
sorry and that is involved in treatment
of alcohol poisoning so ethylene glycol
or methanol poisoning it's administered
to deactivate alcohol dehydrogenase and
prevents poisoning from the buildup of
acetaldehyde and other toxic toxic
chemicals the next drug that you should
be familiar with is disulfiram or
antabuse and you probably heard that the
symptoms of taking this drug and
drinking alcohol are quite formidable in
the sense of a really really bad
hangover and that is because
acetaldehyde dehydrogenase is
inactivated and that results in a
buildup of acetaldehyde and excessive
acetaldehyde is what causes the classic
symptoms of a hangover so usually the
hangover results from having sort of a
backlog in the activity of these enzymes
so we have a buildup of the
intermediaries creating a hangover
antabuse blocks that creating greater
symptoms and ideally prohibiting the
individual from wanting to consume
alcohol because it feels so awful
anyway that's what you need to know on
the base
of alcohol metabolism as far as
nutrition is concerned
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