hi it's mr. Andersen in this podcast I'm
going to talk about carbohydrates when I
say the word carbohydrates you might
think about the starch that's found in
this bread or maybe in this pasta as a
biology teacher I immediately think of
sugar because that's going to be the
building block upon which most
carbohydrates are made but you should
also know that aside from providing
energy for us they also provide
structure and so cellulose that's found
in plants is going to be a
polysaccharide or the chitin that's
found in the exoskeleton of an insect or
the building block of fungi is going to
be a carbohydrate and so they give us
energy but they also give us structure
sugars in science we call saccharides
and the reason I wrote carbohydrates
inside these hexagons is that that's how
sugars are essentially put together and
so if we have just one of these sugar
molecules we call that a monosaccharide
so an example could be glucose if we
have two of them together we call that a
disaccharide an example could be table
sugar or sucrose it's actually one
glucose and one fructose molecule if we
have about three to ten sugar molecules
we call that an oligosaccharide and then
if we have a whole bunch of sugar
molecules attached together we call that
a polysaccharide and so glycogen would
be an example of that and so basically
the empirical formula of all
carbohydrates is going to be the same in
other words we have a ratio of one to
two to one in the amounts of carbon
hydrogen and oxygen so we have twice as
much hydrogen as we do carbon and oxygen
can you see why they're called
carbohydrates we've got a carbon out
here and then we have water so it's a
carbohydrate good way to remember that
if we look at a simple monosaccharide
it's going to have six carbon 12
hydrogen and six oxygen and so the the
simplest the sugar upon which life is
built is called glucose and so glucose
has six carbons we could look at them
there's one here here here here here and
here so there are going to be at the
junction points on this ring in an
aqueous solution or in water they're
going to form these rings but you can
also see that there's going to be a lot
of oxygen so we have all these Hydrox
groups around the outside and that makes
sugars readily dissolvable in water and
so glucose is used in cellular
respiration it's produced by plants and
photosynthesis so they can use it in
respiration so it's the building block a
lot of the different sugars that I'm
going to show you in this podcast are
built upon glucose but there are other
ones we've got the fructose fructose is
going to be a five you can see it's a
five sided sugar it's found it's going
to be a little sweeter than glucose and
it's going to be found like in fruit or
high fructose corn syrup and then we
have galactose and galactose is going to
be a little less sweet than glucose but
these are the basic three
monosaccharides what's cool about these
they all can can readily be moved into
our blood supply and so these are
flowing through your blood right now
these little monosaccharides if you ate
pasta for example we first have to break
that down into its monosaccharides
before we can move it through the blood
and then into the cells in our body so
what are disaccharides then
disaccharides are going to be two sugar
molecules attached together and so the
table sugar that's found in these sugar
cubes is going to be sucrose and so it
is a glucose molecule attached to a
fructose and so when that goes into my
body I have an enzyme called sucres that
has to break that down into its
monosaccharides before I can actually
use it where here's another one the milk
sugar so lactose is going to be a
glucose and a galactose
chemically a track on chemically bonded
together and so if you want to break
down lactose you have to have an enzyme
called lactase now if you're lactose
intolerant what does that mean you just
lack the enzyme to break lactose down
into its two monosaccharides
and so you're going to feel a little
irritation in your gut and that's
because we can't break it down now that
seems to be there's some really cool
studies you could read on on lactose
tolerance or intolerance and it's been
naturally selected in other words if
your ancestors had domesticated cattle
it made sense for them to drink milk
later on in their life but most people
just drink milk when they were young and
so they quit producing that lactase
enzyme okay let's go to oligosaccharides
oligosaccharides are going to be like
three to ten different sugar molecules
they're important in biology in one
pretty important part and that is in the
production of these which are called
glycoproteins so we're in a cell
membrane and these which are going to be
glycol lipids if you look at the glyco
part or the sugar part that's going to
be just a few sugar molecules attached
together and these are really important
for example attaching to the
extracellular matrix they're important
in identifying what type of a cell it is
here's an interesting note I learned on
Wikipedia if you were to eat carrots
carrots are a wonderful wonderful source
of oligosaccharides however you can't
get the sugar molecules out of it until
you've cooked the carrots for about an
hour to release those oligosaccharides
but again if you're not getting them in
your diet we can synthesize those inside
the cell now let's look at this number
right here as we go from
oligosaccharides to polysaccharides and
look how how much that jumped and so
when we're talking about starch for
example what is starch starch is going
to be hundreds of these glucose
molecules attached over and over and
over again and so the starch that's
found in a potato or if we dry it out
it's going to look like this is going to
be hundreds of sugar molecules attached
over and over and over again now why are
plants doing this why are they making
these large molecules they're storing
energy in the starch molecule so they
can use it by chopping it down into
individual monosaccharides now can we do
that you bet we've got glycogen so
glycogen is essentially a macro macro
molecule and so it's going to have
thousands of glucose molecules attracted
together chemically bonded together you
can see what how monstrous this looks
with all these individual glucose
molecules and we're going to store that
in the liver and so if you are carbo
loading what are you really doing you're
eating a bunch of starch you're breaking
those down into monosaccharides and then
you're reattaching those again and
you're storing them in our liver as
glycogen and so we can get to those
stores eventually when we need it we can
chalk chop up those monosaccharides and
we can use them in the cell but we also
get structure remember and so cellulose
that makes up that structure in a lot of
plants you can see here it's going to be
a bunch of sugar molecules attached over
and over again but we're going to have
these hydrogen bonds
cross bond between the different
polysaccharides makes them incredibly
durable if you were to eat wood don't
but you you don't have the enzymes to
break it down inside your gut and so
it's going to go in as wood and it's
going to come out as wood and so if we
want to break down cellulose um we have
to get help and we have to get
microscopic elk and help and so like a
cow for example is going to have a bunch
of bacteria another microscopic life
that lives in their gut that can break
down that cellulose and so they can
eventually get to sugars but it's not
that easy
so how do we do all this building how do
we do all this breaking well there's
basically two processes since it's a
polymer we can use hydrolysis hydrolysis
is simply breaking the sugars and so
right here we have a glucose or excuse
me a lactose molecule you can see it's a
disaccharide and so what we can do is we
can add a water and when we add a water
we can break this bond right here and we
can make two monosaccharides and so
hydrolysis is simply breaking them apart
enzymes help on this as well and then a
dehydration reaction is when we're going
to have two monosaccharides and we go in
the other direction so when we're
actually making lactose we're taking two
monosaccharides we're losing a water and
then we're making that covalent bond
between them and so again we can build
we can make them smaller and then we can
eventually break them down in
respiration now if we were to look at
sugars are they a good thing well
evolutionarily they're very important
why do we love sugar so much it's
because sugar is usually an indicator of
fruit and fruit is going to have a lot
of other vitamins in it that we need and
so humans are essentially programmed to
love sugar sadly what we've done is
we've started to put sugar in everything
and so this I didn't even know this they
made this this is a double big gulp so
if you had this much soda it's made of
high fructose corn syrup
so basically we're enzymatically
breaking down corn to make this fructose
this really sweet sugar and it's killing
us we're seeing an increase in heart
disease and increase in diabetes as a
result of that and so a little bit of
sugar is good we need it for energy
obviously but too much is probably bad
and I hope that was helpful