- [Voiceover] There are several different organic molecules
you'll find within living organisms.
Carbon is probably one of the more important ones.
I mean, the others are very important, don't get me wrong,
but carbon, you a lot of times have heard of humans
as a carbon-based life form.
Pretty much carbon is the building block
of all living things.
It's about 18% of our body weight.
I mean, don't memorize the number.
Depending on the book, it'll be 16, it'll be 20.
It's a range.
But these macromolecules, these components, these pieces,
well, carbon is incorporated to building larger molecules,
things like carbohydrates, lipids, proteins, nucleic acids.
Well, all these larger macromolecules
have to somehow be made, put together.
One way is dehydration synthesis.
And look at the second term, synthesis.
Well, synthesis means to build or make.
Dehydration, remove water.
So the case of dehydration synthesis,
it's removing basically a water molecule to form a bond.
You'll end up removing two hydrogen and one oxygen ions.
What happens, though, is you need energy to do this.
Energy is required to break the bonds
and release the water molecule.
So you build from the small subunits to the larger subunits
to eventually the macromolecules,
things like proteins, lipids, nucleic acids, carbohydrates.
But you don't always want to build.
Sometimes you wanna break them down, release energy.
One way the body obtains energy for the cells is
to break down chemical bonds.
The term hydrolysis, well, you have hydro and then lysis.
Hydro is water, lysis is cut or break.
So hydrolysis means you can add water to break a bond.
When you add water to break this bond,
you're releasing energy.
So pretty much dehydration synthesis
is the reverse of hydrolysis.
Hydrolysis breaks down, dehydration synthesis builds up.
So what you're looking at here is the rough idea
of how hydrolysis and dehydration synthesis work.
If you start in the top right,
notice there is a highlighted H, then a non-highlighted O
then another OH on their side.
What ends up happening is if you take that molecule
plus the one in the top left, you get again
a highlighted OH now and another OH.
By putting energy in the right side
you add energy in and you take out a water molecule.
You form a bond between these two molecules.
But if now you add water back in to the left side
hydrolysis, you add water back in,
it breaks a bond releasing energy.
So it all depends on you trying to build up
larger molecules or break them down smaller.
Dehydration synthesis builds them up
and then hydrolysis breaks them down.
So let's look at carbohydrates to start with.
You might have heard of carbohydrates as
a fast energy source, something that you want
to eat right before a sporting event
to get some high energy.
Well the general formula is
C subscript n H2O subscript n.
What that basically means is if there are
six carbon so C subscript six
there are also six H2O equivalents,
so the Ns are the same.
So you have for every one carbon you have
two hydrogens, to one oxygen.
Now you have smaller types of carbohydrates
called monosaccharides, you might have heard of them
or their simpler term called simple sugars.
Mono means one, saccharides a ring.
So simple sugars are one ring.
Things like glucose, very common sugar in your body.
Fructose, galactose, ribose, deoxyribose,
and those last two ribose and deoxyribose.
Deoxyribose is found in DNA,
ribose, RNA.
Well if you take these monosaccharides
and start putting them together and building
larger and larger, you can make monosaccharides
linking together to make disaccharides,
di just means two.
So you take two monosaccharides they go through
dehydration synthesis, hold that water molecule out,
then you get a disaccharide
two monosaccharides bound together.
You can keep adding more and more and more,
monosaccharides onto its chain.
Just every one you add has to
go through dehydration synthesis.
So sucrose, you may heard of that,
that's glucose and fructose put together.
Maltose, is two glucose molecules put together.
And lactose, glucose and galactose put together.
Where do you find lactose anyway?
Yeah it's in dairy, milks, cheeses, ice creams, yogurts.
So for instance if someone's lactose intolerant
the problem is they cannot take that lactose
disaccharide and very easily break it down
into glucose and galactose.
They're either missing or they don't have enough of
the enzyme that breaks down lactose.
If you're curious the enzyme is called lactase by the way.
Just switch the O to an A, lactase is the enzyme
that breaks down lactose.
So here is your ribose and deoxyribose
so they're both pretty much the same.
Five-carbon monosaccharides the difference comes
into play though when you start looking
at the number of oxygens.
Deoxy means you've lost an oxygen.
So look towards the bottom right of deoxyribose.
You'll see the bottom line has OH
then next to it just an H.
But in ribose both the bottom ones are OHs,
there's your difference.
To show a little more of how things are coming together
or breaking apart, glucose plus fructose
go through dehydration synthesis,
take that water molecule out,
form a bond you get sucrose.
Now don't worry about memorizing all these formulas
it's not that important.
What's more important is knowing
glucose and fructose are monosaccharides,
sucrose disaccharide.
Carbohydrates are ring shaped, or roughly ring shaped.
They have this one to two one ratio.
You're not gonna have to draw out sucrose,
or draw out glucose, or draw out fructose.
Polysaccharides, well we went through
monosaccharides, one ring.
Disaccharides, two rings.
Now polysaccharides have many rings.
I put thousands together here but it could be
hundreds it could be thousands,
it could just keep going, going.
These are huge groupings of monosaccharides
all bonded together.
Starch is a perfect example of a polysaccharide.
Starch is how a lot of plants will store energy.
The plants will take the individual monosaccharides
and then to start to bind them together to make starch.
Glycogen is how us as animals store energy,
it's one way at least.
Glycogen is just a whole series, a mess,
of glucose molecules bound together.
Now the reason it's stored energy is
every bond contains energy.
So anytime you break a bond you release energy.
The glucose molecule also contains energy.
Cellulose another polysaccharide,
it's indigestible you cannot digest it.
You can chew it up as much as you want,
it still comes out as cellulose.
This is more of a structural support for plants.
So as a plant-based polysaccharide get a structural support
something us as humans cannot break down.
So here's what you're seeing with the
dehydration synthesis the formation of glycogen.
One glucose, second glucose, they go through
dehydration synthesis to form
the longer chain of glycogen.
Each one of those monosaccharides,
each one of those individual rings,
was bound to the next via dehydration synthesis.