- [Instructor] This is the
last part of chapter two
in your book.
So we're still on chapter two,
but this is actually the fifth lecture
and therefore the fifth
quiz on organic molecules.
So we still haven't really gotten that far
as far as the organization of life.
We've talked about ADAMs,
why they interact with one another.
We've talked about molecules,
particularly water.
Now let's talk about the most
important molecules for life,
and those are what the building
blocks or organic molecules
as we call them.
And most of us know the food version
of these organic molecules that
we consume on a daily basis.
But there's so much more to it than that.
It's not just about food.
It's about structure,
it's about function.
So there's a lot of things
you're gonna learn new today,
besides just the fundamentals
of what a carbohydrate is
and what a lipid is,
and what a protein is,
and when nucleic acids are.
Now before we get into that,
there's one more property of
water we haven't talked about.
And I didn't include it
in that other lecture,
in lecture four, because it
fits better with this one.
And that is that in organic chemistry,
which is essentially metabolism.
Organic chemistry and
metabolism are the same thing.
It's just all the chemistry
in cells in a living organism.
And we've already talked about metabolism,
the way that which cells
and living organisms process energy,
how they make energy, how they use energy,
that's all organic chemistry is.
The reason why we call it
organic chemistry is because all
of these molecules have at
their foundation carbon.
When we say something is carbon based,
that's what we mean by organic.
Now the word organic today
is used in different ways
from the way in which we grow our food,
and the like.
There's many definitions of organic.
But the way in which we use it in biology,
it literally means carbon-based molecules.
Because you'll see
at the foundation of each
of these groups, carbon,
that ADAM is that at center
to build these biological molecules
that are the building blocks for life.
So where does water come into play?
Because water is not an organic molecule,
but it plays a key role in this.
Water is involved in all metabolism.
That's another property of water
that you're gonna be
tested on in this lecture,
your quiz five, lecture five.
All of the metabolic processes
of breaking down carbohydrates,
assembling molecules into proteins and DNA
and all these things,
water is at its core.
Without water, you don't
undergo these reactions.
So that'll be the first
thing that we discussed today
before we get into each
of these four basic biological groups.
Here are the four groups
which we can categorize
all organic molecules
into and most are familiar.
Everybody has heard of carbohydrates.
What do you think of when
you think of carbohydrates?
- [Students] Breads, grains.
- [Instructor] Breads, grains, sugars,
things of that sort.
But we'll show today that
those are actually the minimum.
The majority of organic
molecules that exist
on our planet are not for food.
They're actually for structure.
Plants and a great number
of animals and other
organisms use carbohydrates
as their skeletal structures
and their support
structures for their cells,
which really can't be used
as a source of energy.
So when we think of
carbohydrates, we think food.
When other organisms
deal with carbohydrates,
yeah, there's food,
but they also use it for
their overall structure.
We don't.
We don't necessarily use carbohydrates
for structural components.
We use other aspects of
biological molecules.
Lipids.
When we talk about lipids,
again, we know about triglycerides.
You're gonna learn the
difference between saturated
and unsaturated fats
today on a chemical level,
and you're gonna learn about
things like phospholipids,
which aren't used for energy,
but are critical for life
because all living things
being made of cells,
will find that the major component
of all cells membranes are
this organic molecule
called phospholipids.
Proteins.
This is probably one of
the most diverse groups.
As such, we're only going
to study the fundamentals
of what proteins are and how they're made.
But in the human body alone,
there are about 400,000,
just the human body alone,
400,000 different proteins.
And that's not including other organisms.
A lot of them have some of
the same proteins that you
and I have, but there's
diversity within all life.
And then of course the nucleic acids.
We usually don't think of food
when we think of nucleic acids.
We don't have diets high nucleic acids.
So what are nucleic acids?
Well, it's pretty much
your genetic information.
It's your DNA and what we call our RNA.
But it also plays another
role in energy transfer.
There's a molecule in
the nucleic acids group
that is essential for
metabolic energy transfer
that we're gonna talk about.
So those are the four groups.
So let's first start with water's role.
These are two concepts
that you're gonna have
two separate questions on,
dehydration synthesis and hydrolysis.
So let's talk about what
they are and what's going on
and there's some more terminology
you're gonna have to learn.
Dehydrate.
What does to dehydrate something mean?
Or when you're dehydrated.
You're lacking water
and this is not hydrating me by the way.
In fact they put so much salt
and other things in the soda
that you're actually dehydrating yourself
when you drink soda.
I still drink it, but you're
not hydrating yourself
when you drink soda with
all of that sodium in it
and everything else.
Your body has to excrete more
water than it actually can get
out of the soda.
Anyway, so when you're dehydrated,
you're essentially are losing water.
Well, in that fashion,
this process called
dehydration synthesis is
the organic chemistry
of how all molecules
are assembled together.
So let's look at some terminology
you're gonna have to know.
Each of the four basic
biological groups has
the building blocks,
which we call monomers.
Mono, what do you think mono stands for?
And I'm not talking about the disease.
- [Students] One.
- [Instructor] One.
Okay.
So monomers are single units.
Now for each group they can vary.
For carbohydrates there
are things like glucose,
for lipids there are things
like glycerol and fatty acids,
for proteins there are
what's called amino acids.
You've probably heard
of amino acids before.
And then the nucleic acids group,
they're called nucleotides.
So the monomers vary in their
overall chemical structure,
but no matter what their
overall chemical structure are,
they are the building blocks
for each of those groups.
So when we build structural
organic molecules,
like our proteins, like our carbohydrates,
when we store it for longterm
energy, triglycerides,
which are the saturated
and unsaturated fats,
these are larger building blocks.
And even your DNA.
In fact your DNA,
the smallest DNA is about
33 million monomers long.
That's the smallest
strand of DNA you have.
So what happens?
Well, when you have these
individual building blocks
that you typically get from your food.
As you're eating your food,
you're breaking down the
proteins and the fats
and the carbohydrates
from other organisms,
and you get this stockpile of monomers.
Well then we restructure
them into the proteins
and the carbohydrates that
we need for ourselves.
So when monomers are assembled together,
then they form long strings of monomers,
which we no longer call monomers anymore,
we call them polymers.
So poly means many.
So dehydration synthesis,
why is it called dehydration?
Because as you can see
here in any reaction,
whether it's proteins,
nucleic acids, carbohydrates,
or lipids, all of these
reactions will remove
a hydroxyl group and a hydrogen atom
from the two monomers and remove water,
and in that process will covalently bond
the two monomers together.
Remember I told you that a
dash means a covalent bond.
So this process is essentially building,
taking smaller units and
building them into larger units.
So if we were to define
dehydration synthesis,
we would say that it assembles
monomers into polymers.
And let me say that again.
So dehydration synthesis
assembles monomers,
covalently bonds them together,
assembles monomers into polymers,
longer chains that in some cases
are hundreds of units long,
and others are millions of units long.
- [Student] The bottom one is a polymer.
- [Instructor] This is
a polymer right here.
Yep.
When you get these long
streams of monomers,
we call it a polymer.
The top part are
the individual monomers
being assembled together.
It is just done over and
over and over and over again.
This is also an energy storage process.
Where you build these together,
you actually store energy.
And we do this during periods of time
when we're not eating,
our body will take some of
the excess food and energy
and assemble it together and then store it
for later periods of time
when we need that energy.
Now, the opposite called hydrolysis.
Hydro again stands for water.
Lysis means to break apart.
So hydrolysis is just the reverse.
It takes polymers,
breaks the covalent bond
between the individual
units by using water
and essentially reverses this process.
It breaks a covalent
bond and it breaks them
into their individual monomers.
So an example of this
is every time we eat.
When we eat starch.
Starch is a long polymer
of individual glucose molecules.
And when we eat that,
our body will start breaking
the individual covalent bonds,
using water and other things
we'll talk about later
in subsequent chapters and break them down
into their individual
monomers like glucose.
That's one of the reasons
why you get such a sugar high
when you have what we
call high fructose syrup,
because the fruitose is a pure monomer.
There's no need to break it down.
Your body just gets instant energy.
And that's why you get the
crash afterwards as well.
So that's why starches and
other large molecules tend
to last longer because your
body slowly breaks them down
and releases energy as you need it.
You don't get this huge spike in energy
where you start going a little crazy.
All right.
So hydrolysis is polymers are
broken down into monomers.
This is what happens
when we extract energy
from these molecules.
This is why we eat, to extract the energy
from these molecules by
breaking the covalent bond
and by doing so,
we get energy out of them.
So let's start
with the one we're all
pretty much familiar with,
and that is carbohydrates.
Carbohydrates, one of the main purposes
of this group is energy.
So don't get me wrong,
even though I say
that it's not the most
abundant carbohydrates,
it's all about energy.
Plants, animals, fungi,
bacteria, they love carbohydrates.
It's the easiest organic
molecule to break down
and get energy from.
That's why we go for the carbs first.
It's because our cells and the way
that organic chemistry works,
it's really easy to get energy from them.
Easier than getting energy from fats.
When you exercise, if you do that thing,
you burn your carbohydrates first
and then your body starts
digging into the fat reserves,
which is why you have to typically work
out for longer periods of
time than just quick bursts,
because your body will say,
well, I got the store of carbohydrates,
I'm gonna go for that first.
Okay.
Now, the name actually tells
you what they're made of.
Carbo has to do with carbon,
hydrates like water, what's water made of?
- [Student] Hydrogen and oxygen.
- [Instructor] Hydrogen and oxygen.
So guess what?
Carbohydrates are made of carbon,
hydrogen and oxygen.
That's their fundamental structure.
So as they get assembled together,
let's look at their
fundamental building blocks,
which we call,
instead of saying monomers now,
we have specific names for each group.
These monomers for the
carbohydrates, these simple sugars,
we call them monosaccharides.
So when we say monosaccharides,
I don't have to tell you
which group I'm talking about.
You know that they are monomers
of the carbohydrate group.
So monosaccharides.
What are some examples of these?
They can vary in their
structure and shape,
but they pretty much
have the same purpose.
They're pretty much used for energy.
There's no other real
purpose for monosaccharides.
They're just energy.
When they start getting
built into larger structures,
then they take on different functions.
But in their monosaccharide
form, it's energy.
The three on the right.
These are the building
blocks for the carbohydrates.
Glucose is by far one of
the more prominent ones
that's used in biology.
But there's others.
Like fructose.
That's what's in most of your
candy and other sugar drinks
and whatnot, high fructose corn syrup.
That's it.
It's just pure fructose monosaccharides
that are being pumped into your body.
And then there's a little
less known called galactose.
So glucose, fructose, and galactose.
These are three types of monosaccharides.
You will not need to know
their structure and their shape
and other things like that.
You just need to know
those three names, okay?
And that they are monosaccharides.
Glucose, fructose and galactose.
Okay?
Now, those are the building blocks.
So let's start building.
When you start undergoing
what we call dehydration synthesis,
which we just talked about,
in the carbohydrate groups,
you take a hydroxyl from one
sugar, a hydrogen from another,
and you covalently bond them together.
So they ended up having
this oxygen between them,
but the covalent bond bonds them together.
Well now that there's two sugars,
we call it a disaccharide.
Di means two.
Now this is the type of
sugar that you typically deal
with when you bake.
We usually don't use
high fructose corn syrup
when we bake.
What do we use?
We use sucrose.
That's table sugar.
That's what you buy at the
store in those big bags,
which we call sugar.
It's actually sucrose or a disaccharide.
Now again this is also used for energy.
We put it in to make things sweet.
Our body can and does break
it down through hydrolysis
into glucose and fructose.
So it's a very simple sugar as well,
but it's not a monosaccharide.
We call it a disaccharide.
There's two other types of disaccharides
that you're probably familiar
with that I'm not even
gonna ask you for sucrose
what the two monosaccharides are.
But let's talk about some examples
of some other disaccharides.
Lactose.
What's that found in?
Milk.
Okay.
So lactose sugar is
also a disaccharide made
from two monosaccharides.
And then there's one more.
Maltose.
Anybody venture a guess
where you might have
that or what it's used for typically?
Like a malt liquor?
It's usually the sugar used
in a fermentation process.
They use the malt in the malting
process for fermentation.
So there's different types
of disaccharides in sugars.
Let's talk real quickly about lactose.
I'm lactose intolerant, severely.
And most people are.
In fact, if you're not lactose intolerant,
if you can break down the
lactose sugars and milk,
then you are a mutant.
Not a very powerful mutant,
but you are a mutant.
I don't think you would
join the X-Men anytime soon
but the reason why you're a mutant is
because the normal process
in humans is we stop
producing a protein called
an enzyme later on when
we reached adulthood,
where we no longer need those
lactose sugars from the milk.
Now there's other things
that you could get from milk
but most of the time we replace milk
with beer or something else.
So we don't need milk.
We need it when we're young
and our body produces that enzyme.
But as we get older,
we stop producing that.
But evolution, we'll talk about,
especially here in the US
has selected for individuals
that do, because of our diet,
have the ability to retain
the function of that enzyme
and therefore break it down.
Now, if you really want to
have your ice cream and milk
without the side effects, you
can go down and buy enzymes,
they're called Lactaid from a Walmart
or any other Walgreens or whatnot,
and they temporarily give you that ability
to break down the lactose
sugars through hydrolysis.
But we'll learn in lecture seven,
when we talk about enzymes,
how if your body doesn't make an enzyme,
you don't undergo that process,
specifically hydrolysis
or dehydration synthesis.
When you lack those enzymes,
there's anything from a mild irritation
in breaking down milk sugars to death
if it's an enzyme that's actually
critical for the function
of certain organic processes.
And this is where inherited
genetic diseases typically come
about is when we're
missing that protein due
to the genetics we
receive from our parents.
It can actually be very life threatening.
Now lactose intolerance
is not life threatening,
but others can be.
Okay.
So sucrose, lactose and maltose.
You just need know them as disaccharides.
You don't need to know
which ones make them up,
that glucose and fructose make sucrose.
I can't even remember which
ones make lactose and maltose.
I know galactose is in here somewhere.
So just know those as disaccharides.
They're also only used for energy.
There's no other purpose
for these disaccharides but energy.
All right.
Now let's talk about the
more complex structures
of carbohydrates, what
we call polysaccharides.
Again these are the polymers.
So anything typically
over about 100 monomers,
we call a polysaccharide.
I make that distinction right now
because at the very end
of this portion I'll show you
one more type of saccharide
that doesn't really fit into
what we're describing here.
So polysaccharide.
There are four that
you're gonna learn about,
and that you'll need to
know for testing purposes.
Well, three out of the four are up there.
So we have cellulose,
chitin, that's the one
that's not up there,
starch, everybody's heard of,
and glycogen, which not
everyone necessarily knows
what it is.
All right.
Let's start with the ones
that we're familiar with,
or somewhat familiar with.
Starch and glycogen.
These are almost identical.
As you can see,
each one of these green
hexagons is a monosaccharide.
So these are long,
long streams of these
monosaccharides attached
through dehydration synthesis.
The four of these polysaccharides, okay?
Starch is how plants
store their carbohydrates.
So that's why plant material
typically is high in starch.
Corn, rice, wheat,
and all these things
have these the starch.
Potatoes and the like
have starches in them
that we use
for eating and whatnot.
But we don't store it,
animals don't store their
polysaccharides as starch.
When we eat the starch,
we break it up into individual
little monosaccharides
and we get energy out of it.
And whatever's left over,
we restructure it through
dehydration synthesis
into a slightly different molecule.
It's a little more highly branched
as you can see called glycogen.
We put that in our liver.
Now why do we do that?
Because in order to maintain
homeostasis in our blood,
we need to have reserves of sugars.
But we don't reserve them
as the individual monomers.
We reserve them as these longer
energy storage molecules,
which we call polysaccharides.
For animals, we store as glycogen.
But the same thing happens.
When our blood sugar starts getting low,
in order to maintain homeostasis,
we start breaking off the
monomers through hydrolysis,
by taking water and
breaking the covalent bond.
And then we reestablish
that blood sugar level.
Okay?
Our body is constantly
spending time to make sure
that we have enough and adequate sugar
in our blood so that it gets
to our brain and our cells and
gets to the rest of our body.
So those are two examples
of long term energy
storage for carbohydrates.
Okay?
Now let's talk about the other two.
Notice the structural
difference of cellulose.
So where is cellulose found?
Well, plants not only
structure their monosaccharides
into energy storage,
but they also use it for
structural support of their cells.
What am I talking about?
Wood, fiber, that's cellulose.
So cellulose is a protective
carbohydrate, very thick,
very tough layer.
I mean, wood is very tough
because of all of these
fibers of cellulose.
Now this is not an energy molecule,
not even for plants.
Why?
Well it gets into the fact
that these are linear
rather than branched.
Again in lecture seven,
when we talked about enzymes,
we'll show that due to the
fact that this is branched,
we can break it down through
dehydration synthesis.
But due to the fact that
cellulose is linear, we can't.
Yeah, the energy's there,
that's kind of the Holy grail of trying
to take plant material
and actually extract it
and make ethanol and things
of that sort, which is a
difficult process to do.
But the energy is there
and some organisms can get energy from it.
For example termites.
In fact, it's not even the termites
that get the energy from it.
There's a little microbe inside their gut
that can convert the cellulose
into monosaccharides,
and then the termite
gets energy from that.
So cellulose.
Let's look at the plant fibers.
They're held together
due to their polarity
by hydrogen bonding.
Here's another example
of how hydrogen bonding
plays its role biologically,
just like water has its attraction
to itself due to hydrogen bonding,
so do the fibers or strands
of cellulose have that weak attraction.
Now collectively becomes very strong.
Individually the hydrogen bonds are weak
but collectively they're strong.
So like celery.
Celery that has a lot of fiber in it.
Not a lot of calories,
not a lot of energy you can
actually get because most
of the celery is water and cellulose.
So fiber is good for your diet,
but you don't actually
get any energy out of it.
Now other things can highly
compact the cellulose
and that's where wood comes into play.
And that's where trees get their
very rigid structure is due
to these massive strands of
interwoven cellulose fibers
that form around their cells
and give their cells a rigidity that you
and I just don't do.
All right.
Now, so cellulose is by far one
of the most abundant
polysaccharides on earth,
because it's the primary
component of plants.
It's the primary structure
that surrounds the plant cells
and gives them their rigidity.
Now chitin.
Everybody wants to say
chitin when they see it.
It's chitin.
Chitin is a carbohydrate
that is primarily found
as the exoskeleton of crustaceans
and insects, crabs, lobsters,
and the insect clade.
This is their,
when you step on something and you hear
that crunch, that's chitin.
When you go to Red Lobster
and you crack open their
shell, that's chitin.
You don't get any energy from chitin.
If you've ever tried chewing it,
you don't get any energy.
You want the meat,
the protein that's inside of their legs
or their body or whatnot.
So that hard shell,
that exoskeleton is pretty much
what protects these animals from--
It's their skeleton,
just like we have an internal skeleton,
they have an external skeleton.
But it's not made of calcium,
it's made of chitin,
which is a carbohydrate.
So that's just another example.
Now chitin can vary in its overall form,
which is why you're not
seeing its structure.
But it's still undigestible
in terms of getting energy from it.
So cellulose and chitin are
what we call structural polysaccharides.
They're not used for energy.
They're used for structure for plants,
for animals that have an exoskeleton.
It's used in fungi.
Fungi do the same thing as plants,
they surround their
cells with carbohydrate,
but they don't do it as cellulose,
they do it as chitin.
That's why fungi are so
resilient in their environments
and so difficult to get rid of is
because they can withstand
extreme environments.
I mean, they live in extreme environments.
They're constantly degrading things
and waste products.
It's not an easy place to get food.
So they need to protect
themselves by covering their cells
with this hard substance called chitin.
All right.
So those are the main groups
in the carbohydrate groups.
Now there's one more.
This one doesn't really fit the mold,
but you still need to know about it
because throughout the semester,
you're gonna be seeing this
when we talk about blood type,
when we talk about organelles of the cell,
like the golgi apparatus and what not.
So it's gonna come up several times.
So it's important that we understand it.
It's not a polysaccharide
because it's not hundreds of units long.
It's not a mono or disaccharide
because it's more than two.
So if it's somewhere in
between about three to 100,
we call it an oligosaccharide.
So what is an oligosaccharide?
Because it's not used for structure,
it's not used for energy.
So what is it used for?
Well, we know that if you need blood,
let's say you have blood loss
or you're donating blood
because or whatnot,
that blood types need to match.
A with A, B with B,
AB with AB, and O, which is
actually a universal donor.
We're not worried about the
RH factor later on the plus
or the minus but the O--
So we know that there's
compatibility and incompatibility
between our cells and
it's not just our blood,
it's our organs.
You do a heart transplant,
you need to have a good donor match.
What is it that they're trying to match?
Well, on the surface of all
of your cells, we have these
what we call oligosaccharides,
which are essentially just three
to 100 carbohydrate monomers
that are covalently bonded to each other.
So what is the purpose?
The purpose is cell recognition.
How do we know when
our bodies get infected
with the bacteria or fungus?
It's because bacteria
and fungus have their
own oligosaccharides.
And when our immune system sees those,
it says, oh, that's not me,
and tries to destroy it.
So as our immune system develops,
we learn to ignore our
own oligosaccharides
and destroy anything else.
And that's why when they
try to find a good match,
a donor for an organ or
for blood or whatnot,
they need to have almost
identical oligosaccharides
on that tissue,
otherwise it's gonna be rejected
by the body's immune system.
So these oligosaccharides
are attached to the surface
of all your cells.
For your blood,
that's how we determine blood type.
If you have one type of
oligosaccharide on your blood,
you might be blood type A.
If you have a different
oligosaccharide on your blood,
you're blood type B.
If you have none of the
ones we usually consider
for blood type, that's what O is.
O is actually lacking these.
And that's why O can be given
to anybody minus the other factors,
the RH factor, the plus, or the minus,
because there's nothing
to recognize as foreign.
That's why O blood type
is the most desirable is
because it's lacking these
recognition molecules
that will be rejected if the body says,
hey, this isn't my blood,
this is some foreign object.
So that's what oligosaccharides are.
They're in all your cells,
they're attached to the
surface of all your cells.
Each person has kind of
a unique set of these.
The more genetically related you are,
the more likely you are
to have these same
structural oligosaccharide,
which is when they look for donors,
they first look for genetic relatives
because it's more likely
to occur within people
who are genetically similar to you.
Lipids.
This one is not as clear
cut as the carbohydrates
because there is a variety of
groups within the lipid group.
It's not like carbohydrates
where there's three monomers
that pretty much build everything.
Lipids, there's a lot of diversity.
The unifying concept of all lipids is
that they are either completely,
or at least mostly hydrophobic.
What does hydrophobic mean again?
- [Student] Repel water.
- [Instructor] They repel water.
They don't like water.
And the main reason for that is
because they don't form
polar covalent bonds
and are therefore neutral.
And water doesn't like neutral substances.
It likes polar, it likes ionic.
So water and oils and
lipids don't mix primarily
because lipids don't
have any charge to them,
and therefore will
separate out from water.
That's why they're hydrophobic.
All right.
So we know about a lot of
the lipids that we have
in our diet, but let's look
at what makes the
difference between saturated
and unsaturated fats.
Those are what we usually think
of when we think of lipids
as far as a food source,
but there are other structures as well
that become important.
So there are four main groups in this.
Two of which I'm going
to primarily focus on.
The triglycerides and the phospholipids.
We'll mention sterols and waxes.
There may be question on sterols,
but the majority of the
questions in this group are
on these two because these
play the most relevant role
in all living organisms.
So the triglycerides
and the phospholipids.
Now, yes we do have monomers
and polymers in this group,
but they're not like the other groups
where you have millions
of monomers put together
to form polymers or even hundreds
of monomers put together to form polymers.
So technically speaking,
dehydration and synthesis
and hydrolysis still apply
to this group, but you're
not gonna see the large,
large structures that are found
in the other four groups
or the three of the other four groups,
the carbohydrates, the proteins,
and the nucleic acids.
Okay?
So as I mentioned,
there's a lot of diversity
within this group.
Now when we think lipids as a food source,
we usually think triglycerides.
Triglycerides are the saturated
and the unsaturated fats in our diet.
So let's look at the
structure of it and then look
at what saturated and
unsaturated actually mean.
So remember I told you how
glycerol is technically a sugar,
but it's only found
in the structural component
of a triglyceride.
That's why we don't
consider a monosaccharide
in the carbohydrate group,
because it belongs in the lipid group.
That's what triglycerides are made of.
So the glycerol is three carbons
with some hydrogen and oxygen.
But really what makes it a
fat are these huge long tails
of carbon and hydrogen, which
we call fatty acid tails.
Now there's three of
them hence triglyceride.
You have the glycerol and three
fatty acids attached to it,
and that's why we call it a triglyceride.
All triglycerides have the
same fundamental structure.
Some can be a little bit longer,
some have little bit
longer chains than others.
They don't always have
the same exact length.
But notice that they're very simple.
They're just carbon and hydrogen chains.
Remember carbon and hydrogens
share covalent bonds equally.
And that's why this molecule
has no polarity to it,
has no charge to it.
It is absolutely neutral,
and that's why water and oil do not mix.
All right.
Now, what is saturated
and unsaturated fats mean?
Well, it has to do with
the covalent bonding
of the fatty acids tails.
If all of the carbons are single,
covalently bonded to each
other and they're saturated
with the hydrogens,
that's what we call a saturated fat.
It's when the tails
of the triglyceride
have the maximum number
of hydrogens attached
to the carbons, okay?
But occasionally you'll get fats
that have double covalent bonds in them.
Well what that does is
because these two carbons
are sharing four electrons
instead of just two,
that reduces the number
of bonds it can form with other atoms.
Hence you get these gaps where
there's no hydrogen bound
to the carbons,
and so they're unsaturated.
Now we have monounsaturated fats,
we have polyunsaturated fats.
That just tells you
how many double covalent bonds there are.
If there's one, it's
a monounsaturated fat.
If there's many,
it's a polyunsaturated fat.
So structurally, what's the
difference between these two
and where do we find them?
Well, here's this kind
of a bubble filling model
of a saturated fat.
Notice all of the tails
are perfectly linear,
they're all saturated with hydrogens,
and it's very compact.
These are what we would
consider beef fats,
the more solid fats.
Lard and the like
that really aren't as
good for you health wise,
because though they pack a punch,
they've got a lot of energy to them,
they're harder to digest
than the unsaturated fats.
So saturated tend to circulate
through our cardiovascular
system more often,
they have a higher chance
of being deposited in our arteries
and causing clogs and things of that sort.
But pound for pound, fats
have twice the amount
of energy as carbohydrates.
I mean look how mighty
covalent bonds there are here.
And every covalent bond
gives you potential energy.
So that's why though,
if you have a pound of
sugar and a pound of fat,
you're gonna get twice the
amount of chemical energy
out of the pound of fat,
because of how condensed
it is and how many
of those you can have.
All right.
So what does an unsaturated fat,
especially polyunsaturated fat look like?
It looks like this.
So because of the double covalent bonds,
the tails are no longer linear.
They're just kind of all over the place.
Well that creates a less,
they're less dense and
therefore more fluid.
So unsaturated fats are things like oils.
They're much more fluid
and not as compact.
Now these are much easier to break down
and don't spend as much time
in our cardiovascular system,
which is why these tend
to be more good for you.
And you're not losing yourself
up on the inside with oil
so it's not how it works.
But you wanna think about it that way.
Think about it that way,
that they're better for you.
Now, can we turn in a
polyunsaturated fat into a saturated?
Absolutely.
That's what margarine is.
Margarine is where they
hydrogenate the triglyceride.
Meaning they break the
double covalent bonds
and they add hydrogens to it,
thus turning it into a saturated fat.
So what is margarine?
It's a solid oil.
That's why I don't touch the stuff.
It's just nasty.
So margarine, there's pros
and cons to all things.
Due to the chemical process
where they create these trans fats,
it makes it very difficult for
the body to break them down.
So anyway, we won't get
into all the health reasons or whatnot.
But as far as fats go,
the saturated fats are
things like the cheeses,
and the ice cream, and the lard,
and the butter and whatnot
where when you get to the
oils that you get from seeds
and other parts of plants and
other tissues and whatnot,
those are the unsaturated fats.
So that's probably the main
difference between the two.
It comes down to the overall
number of covalent bonds
between the carbons and the hydrogens.
The more double covalent bonds there are,
the more fluid the triglyceride is,
and there's where you get the oils.
Okay.
Now, that's our food source.
Now notice they're put
together in the same way
that the other molecules we've talked
about are put together.
The individual monomers
are the fatty acids
and the glycerol.
When you remove water
from each of these bonds,
that's dehydration synthesis,
you covalently bond them together
and you make a triglyceride.
So in that fashion,
you still have dehydration synthesis.
So what's hydrolysis?
Well we do the opposite.
We come in here, we break
these covalent bonds.
So when you get a
triglycerides in your diet,
first you break off all
the fatty acid tails,
then your body comes in
here and starts chopping
off these covalent bonds
through hydrolysis,
and those two carbons
actually pact quite a while.
You get quite a bit of energy from that,
which is why fats give you
more energy than carbohydrates.
And that's why your body,
it's a little harder to get at,
which is why it says no, I'm
gonna keep that in reserve.
So triglycerides are good
for long energy storage.
And yes, you do form triglycerides
if you have too much sugar in your body.
And it all depends upon
the individual's genetics
and their metabolism on how
fast they convert excess sugars
into not only glycogen
but they can reconvert the
carbohydrates into fatty acids
and yes, you can increase your fat tissue
by just eating carbohydrates.
You don't have to say,
well, this is low in fat.
So anyway, there's always
trends and other things
and I just try to dispel
some of these myths.
All right.
Phospholipids are almost identical
in their overall structure
to triglycerides.
Let's break it down.
It has a glycerol, just
like a triglyceride.
It has fatty acid tails.
And those tails can be saturated
or unsaturated just like triglycerides.
But instead of having
one more fatty acid tail,
which is why we don't
call it a triglyceride,
attached to that third
carbon is a phosphate
and a nitrogen group.
Now this is what makes this
molecule not only unique,
but essential for life is that group,
that phosphate and that nitrogen group.
The phosphate group is negatively charged
and the nitrogen group
is positively charged,
which creates a polarity to this head.
And we call this portion
of the phospholipid the phosphate head
or the hydrophilic head.
When something is charged,
it likes water.
So this molecule has a personality crisis
so to speak, because the
majority of it hates water.
These hydrophobic tails
being neutrally charged,
don't like water one bit.
But this head loves water.
So what happens is when
you put phospholipids
into a watery environment,
remember all living
things are mostly water,
it does this.
It creates these bilayers.
Two layers of phospholipids,
where the heads are oriented
on the out and inside of the cell,
and the tails are oriented
on the inside where
they're not near water.
This creates a fat layer
that protects the cell.
We call this the cell membrane.
And all cells have it,
which is why this is one of
the most crucial molecules
for life is because all
cells are surrounded
by these phospholipids
bilayers as we call them.
And that's what helps
separate the external
and internal environments of the cell,
where it's able to maintain homeostasis.
Every living organism has these.
This is not used for energy.
It is purely for structure.
All cells have this.
Not only on the outside,
but as we'll learn in the next lecture,
on the inside as well.
These phospholipids form the majority
of what we call organelles
or the organs of the cell
that each have specific functions.
The majority of them have
at their foundation, these phospholipids.
So it forms a very important
structural component
for the outside of the cell
and the inside of the cell.
Now, less talked about,
but still important to look at,
this is where things started
getting a little crazy
because unlike triglycerides
and phospholipids, sterols
are totally unique.
They do not have even
close to the resemblance
of what triglycerides
and phospholipids have at
their fundamental structure.
And these really don't form polymers.
This group, the sterols
and the waxes don't
really form huge polymers
or even close to the polymers,
like triglycerides and phospholipids.
So what are sterols?
We usually think when
people think sterols,
they think steroids.
And those are actually different.
So don't confuse the two.
Sterols and steroids are different.
So what are sterols?
Well, they're fats because
they fit the definition
that they are hydrophobic.
But notice their structure.
It has no resemblance to the triglyceride.
So what does it look like?
Well the main fundamental structure
of all sterols is
what we call a four
fused hydrocarbon ring.
Okay?
Just remember that word.
Four fused hydrocarbon ring.
It's not even like sugar.
Sugars have these big gaps
in oxygen in between
them and form these long.
These are actually fused together.
That's why we say four
fused hydrocarbon rings.
What is the most prominent sterol?
Cholesterol.
So cholesterol is not a
triglyceride, but it is a fat.
And our body uses it
for a number of things.
It uses it and puts it
in our cell membranes
to increase their fluidity,
we put it in other parts
of a cell as a hormone
so to speak,
and we convert it into various hormones.
Cholesterol gets turned into
testosterone and estrogen,
which are also sterols.
So testosterone, we know about,
estrogen, we know about.
By the way,
the myth that there's more
estrogen or testosterone
in male or female,
let me just take that away.
Men in your testes,
you have a higher
concentration of estrogen,
which is used
to create your sperm than
women have circulating
through their body.
So we use both,
women use both testosterone and estrogen.
Yes, there are differences
in where we use them
and how we use them,
but ultimately testosterone
and estrogen are both in male and female.
Just depends upon where you look.
Vitamin D, cortisone.
Cortisone is an important hormonal signal.
And vitamin D plays a key role
from our skin being activated by light,
and then creating the
vitamin D that we need
for various aspects of our body.
But not all organisms
typically use sterols.
You don't get bacteria using testosterone.
You don't get other microorganisms
using a lot of these.
So that's why it's not
necessarily talked about as much,
but it is important to at least understand
that cholesterol is not a triglyceride.
It's a sterol as we call it.
Now I have got some beehives.
So I love talking about this.
I forgot to bring in my comb.
Usually when I do, people start ruining it
and they squish it and whatnot.
I'll bring it in next time.
The waxes are also again very unique.
Now they are lipids,
but there's somewhere
in between a saturated
and unsaturated fat.
And they're not really triglycerides.
They do have fatty acid tails,
but they are combined with alcohol
or other carbon structures.
So what's so important about waxes?
Well they are hydrophobic
and they're great
for like in the bees for
storing the liquid honey.
We use wax in our ear
to be able to collect
and prevent organisms and such,
help with dust and other
things that's necessary.
But not all organisms use waxes.
So wax, that's why you're
not even seeing the structure
here is a water repellent,
pliable substance.
So it is hydrophobic,
and it's used in very
unique circumstances,
but not all organisms
necessarily use them.
That's why this one's kind
of an odd ball as well.
The proteins group is the most diverse
of the four basic biological groups.
In the human body alone,
you have 400,000 different proteins.
That's a lot.
And so ultimately, the question becomes
what are the fundamentals
of the protein groups?
Since we can't go over all 400,000,
what makes a protein a protein?
What are the fundamentals?
All right.
So let's start with the
basic building blocks.
Monomers.
What are the monomers
of the protein group?
Well we call them amino acids.
Now you've heard of amino acids before.
Typically you hear
about them in nutrition,
where you talk about essential amino acids
and non essential amino acid.
Let me tell you the
difference between them.
Essential amino acids are amino acids
that you can't make yourself.
So you have to get them in your diet.
You cannot manufacture
them through metabolism.
So you have to get them in
the food that which you eat.
Non essential acids are
ones that you can make
from other molecules that
you consume on a daily basis.
So that's really the
difference between them.
You have your essential ones that you need
to get through your diet, and
then your non essential ones,
which you can manufacture
in your own cells.
So what is an amino acid?
Well, the name,
it gets its name because
of the chemical groups
that are universal for all amino acids.
On one end,
you have a nitrogen and two hydrogens
which we call an amine group.
And then you have a
carbon which is attached
to in the center,
and then on the other
end of that carbon is
what we call a carboxyl group.
Now, without into the
details of how this is done,
the carboxyl group actually
releases a hydrogen ion,
which makes it an acid, hence amino acid.
That's why they're called amino
acids because all monomers
of the protein group,
all amino acids have this
fundamental structure.
Now what's this R group right here?
That's what makes amino acids different.
There are 20 amino acids
that all living things use
as their building blocks.
They are the universal building
blocks for all proteins.
In some situations, it might
be a simple hydrogen atom.
That's one of the most simple
amino acids called glycine.
In other situations,
they might be huge carbon ring
structures with some nitrogen
in them as well, like tryptophan.
Here's another one called cystine.
You're not gonna have to
memorize any of the amino acids,
but these are just some examples
of how amino acids can vary substantially.
And there are 20 of these building blocks.
So let's look at how they're put together.
No matter what we call R
or functional group is,
they all have the same basic fundamentals
of how they're assembled together.
Same processes we talked about before.
Hydrogen and hydroxyl group get removed
through dehydration synthesis
and the covalent bond exits.
Now, the book and others
will refer to this
as a peptide bond, but
it is not a new bond
that you haven't learned.
It's a covalent bond.
Why do they call it a peptide bond?
Because chemically, chemists
because of the nature
of this bond, call it a peptide bond.
So the reason why I point that out is
because it makes it easy to understand
what the polymers of all proteins are,
they're called polypeptide chains.
That's the universal
word for all proteins.
All proteins When they're
assembled together
from their monomers
into a polymer, we call
them a polypeptide chain.
It doesn't matter which
protein you're talking about,
all proteins are polypeptide chains.
Essentially, just long strings
of amino acids assembled together
through dehydration synthesis, okay?
So make sure you understand
peptide bond is no different
than a covalent bond, it's
just how chemists name it.
Now the same process
occurs when we eat proteins
for a food source.
We break them down through hydrolysis.
We add water, we break the covalent bond,
we get energy out of it.
So we can get energy out of proteins
and carbohydrates and fats.
Well, what's interesting
about proteins is not
that they're not just for food,
they're not just for energy,
but they're what make you who you are.
Let's look at the composition
of what actually is a protein.
Proteins are not just
simple linear structures.
There is a three dimensional
shape in which they fold into
that gives them a very
unique role in the cell
or in your cells.
Let me give you an example.
We know that wrenches and
screwdrivers are tools
that are used for various jobs.
They pretty much made
of the same material.
Fundamentally they're made of metal.
But based upon what mold they were put
into when that metal was shaped,
will determine what job they can do.
You can't use a wrench for
what a screwdriver would do,
and you can't use a screwdriver
for what a wrench would do.
And the same thing
applies to proteins here.
Proteins essentially have
this hierarchy of folding
that is based upon their ability
to covalently bond, hydrogen bond,
and here's where we
get some ionic bonding.
Yes, there is some ionic bonding
in the protein structure.
Remember we talked about ionic
bonds, typically don't form,
but this is the one exception
where in some scenarios,
when the protein folds,
there is some ionic interactions
between the protein chains.
So let's look at this hierarchy,
because this is what
I'm gonna test you on.
The primary structure of a
protein is essentially the order
of the amino acids.
Now, the order is just
what order do they get
covalently bonded in?
Alanine, threonine, cystine, tyrosine,
glutamate, glycine and whatnot.
What order do they get put in?
Well just like you understand
how in the English language,
the different order
that the letters are put
in have different meaning for the words,
the same thing is true for proteins.
What order are the amino acids
going, are covalently bonded
to each other,
predetermine how that
protein is going to fold
and therefore function.
If you put them in the correct sequence,
then they will fold
properly into that globular
or three dimensional shape,
like a wrench or a screwdriver
so to speak as I gave you that analogy.
But all the primary
structure is, is the order
of the amino acids.
Nothing else.
How do we get that order?
Well this is the relationship
between your genetic
material and your proteins.
Your DNA, which is found
in all of your cells,
has that template that tells your cell
what order to put the amino acids
in and therefore how
to make your proteins.
So in lecture 10, so ways off,
but lecture 10 is when we're going
to discuss very deeply this
relationship between how you go
from the blueprint to the actual house.
It's kind of the difference
between having a blueprint
of a house and the actual house itself.
The DNA would be the blueprint,
the house would be the protein.
That's how you construct it
as your blueprint tells you how to do so.
Now the secondary structure
is where you start
to get initial folding.
It's not quite ready at this point,
but you do get some of the--
Think about origami.
In the initial stages,
you're just kind of folding it.
It does have some dimension to it,
but it's not what you want it to be yet.
It's just the initial stages of it.
So you start getting these
loops of these little sheets
and whatnot, but proteins
really don't function
on that level.
Now where does the secondary
structure come from?
It primarily comes from
the hydrogen bonding
because amino acids,
like other molecules
have polarity to them.
Now there are some amino acids
that are neutrally charged,
but there are a lot of other amino acids
that have a polarity to them.
And then there are some
amino acids that are ions.
So there's a great amount
of variety of amino acids.
Some are neutral, some
are positive charge,
some are negative charge,
some are polar,
which they have both charges.
There's a great deal of dynamics.
So you can see here that these loops
and sheets actually form
because of the polarity
of these amino acids.
Like water and like
carbohydrates and whatnot
as I showed you,
this is another example
of hydrogen bonding
as it exists in biology.
Well once you get through
the initial secondary stage
or secondary structure of folding,
then we get to the most important one,
which is what we call
the tertiary structure.
So what's a tertiary structure?
So essentially the three dimensional shape
that the protein will take on,
and that gives us its function.
This is the difference between
the wrench and a screwdriver
and a hammer.
They each have respective jobs,
even though they're made
of the same material
and one can't do the job of another.
Okay?
So tertiary, you'll see
on the quiz times the use
of the language three
dimensional or globular,
those all mean the same thing.
So tertiary, globular, three dimensional,
these are all space filling models
of how the protein is structured.
This is pretty much how
all proteins function
on this level, is this tertiary structure.
And we'll give some examples of these.
Now the last one isn't
actually much different
than this one.
It's called quaternary structure.
What is quaternary structure?
It's essentially multiple
polypeptide chains,
all combined together
into an even larger three
dimensional structure.
So the only difference between a tertiary
and quaternary structure is
how many polypeptide chains you have.
For a single tertiary structure,
it's just one polypeptide chain folded.
But for a quaternary structure,
a perfect example of this is hemoglobin,
which is in your blood.
Hemoglobin actually has four
different polypeptide chains,
each individually folded,
and then what holds them
together in the middle?
Iron.
That's why you have a lot
of iron in your blood.
So there's some iron that
holds these four together.
That's what carries your
oxygen and your carbon dioxide
through your blood.
Okay?
So the only difference
between these two is just
how many proteins are involved?
How many polypeptide chains?
So if you see me describe
multiple polypeptide chains
forming a larger structure,
that's quaternary.
But as you can see,
they're really not much
different than each other.
In fact, this is generally the rule.
This is generally the exception.
There are more proteins
that form these higher conflict structures
in your body than single proteins.
Now this is just to give you an example
of some of the proteins.
You're not gonna have
to memorize any of these
but some of these will come up quite a bit
throughout the semester.
So it's a good and important
to at least give you a preview
about what we're doing.
Muscle.
Your muscle cells have two major proteins.
There's actually more than
two, but two major protein,
actin and myosin,
which interlink and
ultimately are the proteins
that cause the force of contraction.
So your muscles,
which are cells are able to function
because they have an
abundance of these proteins.
Antibodies.
Your body produces 10
million different variations
of antibodies to try to respond
to any infectious disease.
Carbohydrates, lipases, proteinases,
this is a huge group we're
gonna spend a lot of time
on lecture seven called enzymes.
Guess what's actually doing
the dehydration synthesis
and the hydrolysis.
It's enzymes.
So there are proteins
that are actually putting
molecules together
and breaking them down.
So it's not just happening
spontaneously in your cells.
These enzymes are what
actually break it down.
If you remember I talked
about lactose intolerance.
People who are lactose
intolerant can't break
down the lactose sugars because they fail
to produce this enzyme that does that.
And no two enzymes do the same job.
Each one has their own tertiary structure
and therefore does only one job.
It's like trying to take a
wrench to do a screwdriver's job.
It just won't work.
Okay?
So each protein has a specific job.
If you don't make that
protein, you don't do that job.
In some cases it just
causes a mild irritation
of milk proteins.
In other cases, it can
be life threatening.
So, let's see, insulin.
Insulin is a protein we're
gonna talk about quite a bit
because it's necessary
for your body to maintain
homeostasis and pull glucose
out of the blood stream into your cells.
We know if you have type 1 diabetes,
your body doesn't produce insulin,
and so you have to have insulin injections
to regulate your blood glucose levels.
Type 2 diabetes is your body
doesn't respond to insulin
and there are other
mechanisms such as exercise
that can actually help
mitigate the absorbance
of glucose into your bloodstream.
Keratin.
Keratin is one of the
more diverse proteins
because it's found in so
many different tissues
in your body and it can be compacted
in any number of different ways.
It forms your hair, it's in
your skin, it's in your nails,
it's in the horns and beaks
of various other organisms.
So it can be really, really tough.
It could be slightly tough.
It can be very pliable like in your skin.
It can be tough like in your nails.
There's many other things,
but keratin has pretty much one main job.
It's a waterproof protein.
And that's why your skin has
so much of it and your hair,
and your nails.
It's very tough and it's very
water waterproof and it helps
to maintain homeostasis for your skin.
So there's just so many
different proteins.
We can't go through them all.
Now, this is the last concept
though that you will be tested on.
And this is the reason why
we'll explain it's not good
to let your fever go up to about 105, 106
if you have a fever.
Your body artificially resets
your internal thermostat
when you have a fever
because a slightly higher
temperature increases metabolism,
and that helps your body to be able
to fight off the infection.
That's why you get a fever.
However, it shuts off
your ability to sweat
and as your body temperature rises,
when you get to a certain point,
there starts to become an issue.
Proteins will only remain
stable at certain temperatures.
If the temperature starts to go higher
and higher due to the heat,
the proteins will actually
start shaking and disassembling
in that tertiary structure.
Remember hydrogen bonds are weak.
And so what happens is if you
raise the temperature enough,
then the proteins do this.
They essentially unravel.
Now what they don't do is this.
They don't snap back together.
Okay?
It's not like a rubber band.
If they unravel, the cell has to chew them
up through hydrolysis and
remake them all over again.
When your cells get too hot,
like when you have a fever,
your proteins undergo this process.
We call it denaturing.
So you're gonna need to know
what denaturing is as well
as what can cause the
denaturing of your proteins.
So denaturing is essentially
a loss of its quaternary
or tertiary structure.
It goes back to this.
It just unfolds to its primary structure.
It's like melting down a
wrench or a screwdriver.
You have this molten metal
that doesn't do anything
because it doesn't have any
shape or any structure, okay?
That's why you don't want your
temperature to get too high
because when the proteins denature,
the cells can't do their
job, the cells die,
and then you start having
massive issues from there.
Now, temperature isn't the only thing
that can actually be nature your proteins.
That's one thing that can
disrupt the hydrogen bonds.
Guess what?
Since proteins are also held
together by some ionic bonding,
as well as hydrogen bonding,
if you change the salt
concentration, sodium chloride,
potassium, calcium, any
number of different ions,
if you increase it too much,
then it disrupts the hydrogen bonds
and the protein falls apart.
So proteins in too high
of a salt solution will
cause them to denature.
They'll break apart.
So it's not just about heat.
And the last one is pH.
Remember all pH is, is a measure
of the hydrogen ion concentration.
Well, proteins are designed
to work at very specific pH.
Not all proteins work at a neutral pH.
Some could work in very
acidic environments.
Like a pH of 2.7, some work
in more basic environments,
like a pH of eight or nine.
Each protein is specifically designed
to work at a specific pH.
So if you change that pH
by adding hydrogen ions
or adding hydroxide ions,
the same principle applies
as it does with salt.
The ions, the hydrogen and
the hydroxide will disrupt
the hydrogen bonding of the proteins
and cause them to denature.
So changes in pH, changes
in salt concentration
and changes in temperature,
pretty much heating things up.
If you cool things down
you can stop the proteins
from moving, but that's
how we preserve proteins
for long periods of time.
They don't denature by freezing them,
but they do denature by heating them up.
So I will test you
on what things can actually
cause denaturation.
So what things don't
denature your proteins?
Well, let me give you a prime example
that you'll probably see on your quiz.
Light.
Light doesn't denature proteins.
In fact, it protects us.
We have a defense mechanism.
When you go outside
and you're exposed to not
only sunlight, but UV light,
your body reacts by producing a protein
that absorbs the light called melatonin.
Not melatonin.
Melanin.
Sorry, melanin.
Melanin production.
So melanin is produced by
your melanocytes in your skin
that's why your skin gets darker.
It's a defense mechanism.
Why?
Because UV radiation can damage your DNA.
And so your cells produce
this protein, melanin
to absorb the light.
And they're not denatured by that.
So that's just an example
of something you would look
for on this one where I say,
which is the bond would not
cause your proteins to denature.
One might be freezing them.
That doesn't cause them to denature
or exposing them to UV light
or even just regular light.
Doesn't cause your proteins to denature.
In fact, we are kind of light driven.
Vitamin D production,
we need light for that to occur.
So we do need some sunlight
to be able to remain healthy
and maintain homeostasis.
But UV light is damaging and
that's why your body reacts
to it by producing the melanin.
Now, last organic group, nucleic acids.
Here we are coming back
to where I mentioned
that there are some sugars
which are technically carbohydrates,
but they don't form the building blocks
of the carbohydrate group,
which is why we don't include
them into the monosaccharides.
Two of those sugars are
called deoxyribose and ribose,
and that's where DNA
and RNA get their names.
DNA literally stands for
deoxyribonucleic acid
and RNA stands for ribonucleic acid.
So the names are derived from the sugar
that makes up their monomers.
Now, the sugars aren't
the only thing that makes
up their monomers.
Here is the basic building blocks
of all DNA and RNA molecules.
There is a phosphate group, a sugar,
which will differ between DNA and RNA.
DNA uses a sugar called deoxyribose,
RNA uses a sugar called ribose.
And then this is the key part right here.
The nitrogenous base.
This part of the monomer is
what provides the information.
Okay?
Your DNA and RNA are pretty
much just blueprint molecules.
They're blueprints for how your cells need
to make the proteins
to be able to function.
So I'll explain in a second
how that blueprint works,
but this monomer, we have
a specific name for it.
It's called a nucleotide.
So make sure you understand
that that is the monomer
of the nucleic acids group.
It's called a nucleotide.
So what makes up a nucleotide?
A phosphate group, a sugar,
and what we call a nitrogenous base.
Now there are many different types
of nitrogenous bases.
For DNA there's four and RNA there's four.
And they share most of them in common.
Though there are some subtle differences.
DNA uses--
Now the reason why we call
them nitrogenous bases is
because they got a lot of nitrogen
in them and carbon and
hydrogen and whatnot.
So DNA uses four basis called guanine,
cytosine, thymine and adenine.
RNA on the other hand doesn't use thymine.
It uses guanine, cytosine,
adenine and it uses uracil.
Now this is just a precursor.
You're not gonna have
to memorize these yet,
but in lecture 10 you will.
So might as well learn them now.
But DNA and RNA are
almost exactly the same.
They just have one base that
they don't share in common.
DNA exclusively uses this base,
RNA exclusively uses this base
but the other three,
they both use as far as their nucleotides.
So if the nucleotides are the monomers,
what are the polymers?
Well, by the nature of saying DNA and RNA,
those are the polymers.
What do I mean?
The shortest strand of DNA
in any one of your cells is
33 million nucleotides long.
Yes, million.
They're the one of the longest polymers
in your body.
And some of your chromosomes have
as much as 100 million
nucleotides to them.
So between, if you count
up all of the nucleotides
in a single cell,
you have about 5 billion
nucleotides for every cell.
Okay?
So this is by far,
one of the more important
organic molecules
because of the data that it holds,
the blueprint that it holds.
Now there are some fundamental
differences between DNA
and RNA and their structure.
Let's look at those.
DNA is your genetic hereditary material.
This is one aspect that
I'll test you on for DNA.
It is what gets passed on from
one generation to the next.
You have a baby, how
do you make that baby?
I don't know if you know
how to make that baby,
but you're fusing the DNA
between two individuals.
So men will pass on half of
the DNA through their sperm,
women will have the other half
of the DNA and their oocyte
or the egg.
When that fuses together,
that's the genetic
material that you pass on.
This is about reproduction.
But RNA is a messenger molecule.
It tells the cell,
it gives the cell the
information that's contained
on the DNA.
So you'll understand more
about this in the next lecture
when we talk about cell
biology and where DNA
and RNA are found and whatnot.
But DNA is kind of like
having this huge cookbook
with all the recipes in it.
Well, when you're making
your brownies so to speak,
you don't want your kids to start messing
up your original recipe.
So what do you do?
You make a copy of that page.
You don't care if that
gets exposed to the flour
and the sugar and the markers
and all the good stuff
that your kids are doing
when you're baking your brownies.
That's really the main difference here.
DNA is the hereditary material,
RNA is just a copy of portions
of your DNA to tell the cell
what to do.
Notice that RNA is just a single strand
and DNA is actually this
double helix structure.
And this provides greater
stability for this
to be a longterm information
storage molecule.
Notice how it's held
together in the middle.
What do you think is holding
the two strands together?
Hydrogen bonding.
Okay?
So individually again,
hydrogen bonding is weak
but collectively it's
what holds the strands
of your DNA together.
Now how are these assembled together?
The same process we've talked
about, dehydration synthesis.
So here's one nucleotide,
phosphate, sugar, and a base.
It then is covalently bonded right here
to the next nucleotide,
phosphate, sugar, base.
Covalently bonded here
to the next nucleotide,
phosphate, sugar, base,
all the way down the line.
So the backbone of DNA and RNA is actually
where the covalent bonding
occurs for dehydration synthesis.
The middle of the DNA is actually
just held together weakly
by hydrogen bonds.
Now why is that important?
Because in order to copy DNA,
it's like opening up a book.
It has to be able to be open
and accessed very easily.
As such, the DNA has to be separated
and then put back together very easily,
which is why it needs hydrogen bonding
instead of covalent bonding.
Because the DNA is constantly
being opened and closed,
open and closed.
Now there's one more molecule
in the nucleic acids group
besides DNA, RNA.
And it doesn't play its
role in information.
It plays its role in metabolism.
What am I talking about.
It's called ATP, adenosine triphosphate.
Why is this a nucleotide?
Well, let's look at it.
It's made up of a phosphate,
a sugar, and a nitrogenous base.
A nucleotide.
So that's why it belongs
to the nucleic acid group.
Now later on we'll discuss
all the ins and outs of this.
For now just accept
that this is the battery
that fuels all metabolism.
When your cells need energy,
this is what they tap into.
You're like, why isn't it a glucose?
Glucose gets turned into this.
Lipids get turned into this.
Proteins get turned into this.
So we'll discuss in lecture
seven, how that's done.
But that's really what ATP is.
It's that double A battery
or that triple A battery
or whatever battery
that plugs in to every
metabolic process in your cell.
So that's why this is
also an important molecule
to understand, it is a
nucleic acid or a nucleotide
because its fundamental
structure is a phosphate,
sugar and base.
We'll talk more later about
what those other phosphates are and why.
So now you know ATP, DNA and RNA.
These are all nucleic acids.
Now ATP is a monomer.
It is not a polymer.
It's just a single unit.
So ATP is an example of a monomer
of the nucleic acid groups
where DNA and RNA are the
examples of the polymers.
Now RNA isn't usually as long as DNA.
RNAs can range anywhere
from several hundred to
several thousand nucleotides.
So they're still pretty long.
They're not millions of
nucleotides long like the DNA,
but several thousand is still pretty long.
So RNA and DNA are the
polymers of that group.
