B2 High-Intermediate 2216 Folder Collection
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Hi. It's Mr. Andersen and welcome to Biology Essentials video 42. This is on
biological molecules or sometimes we call those macromolecules. This right here is a
picture of DNA that's been extracted. We do this every year in AP bio. We take DNA out
of a banana so you can hold it and wrap it around a little nichrome wire. Where is DNA?
Well DNA remember is going to be found in the nucleus. And so to get to it in our lab
we use soap to dissolve through the lipids in this membrane, this membrane. We filter
out the proteins and then we eventually can add it to cold alcohol and it will come out
of solution. You can hold it on a little nichrome wire, the secret of life. But to get to it
we have to go through all of the other macromolecules. In other words nucleic acids, like DNA and
RNA, are just one of four different types of macromolecules. And so in this podcast
we're going to spend a lot of time talking about the other three. And so biological molecules,
there are four different types, nucleic acids, proteins, lipids, carbohydrates. You simply
have to memorize those and then memorize the monomers. So what are monomers? Well monomers
are the small building blocks that make up these biological molecules. In other words
the analogy I'll give you is those are like the letters that string together to make the
words or even the stories. Biological molecules. Now let's start with lipids because lipid
are not actually made up of monomers. They're simply one monomer. Why are lipids important?
Those make up all of the cell membranes but they're also a great source of energy. And
what's a defining characteristic about them is that they have polarity. In other words
they're generally non-polar but certain parts of certain lipids can actually be polar. Let's
go to nucleic acids then. Nucleic acids are going to be the DNA and the RNA. The building
blocks of those are nucleotides, which are simply a sugar, a phosphate group and then
a nitrogenous base. Why are nucleic acids important? Well they carry genetic material
and they pass it from generation to generation. Next are the proteins. Proteins really make
up almost everything that you're looking at right now. When you're looking at me, I'm
mostly made up of proteins. Proteins, the building block of proteins are going to be
amino acids. And what makes amino acids different is going to be their r group. It's just a
portion of the amino acid that differentiates them from the other amino acids, but gives
them really important characteristics in the structure of a protein. And the structure
of the protein is what's important. Remember lipids don't have monomers, but carbohydrates
or the sugars are going to be the monomers of carbohydrates. So starch is an example
of carbohydrate, but regular sugar like glucose is a carbohydrate. Building blocks are going
to be sugars and depending on where we build off of those, where the bonds come, we can
get different structures of sugar. Give us energy, lipids are are going to make up those
membranes, proteins make us and nucleic acids are going to give us the genetic material.
Now if you have monomers, when we stack those monomers together, there's going to be clear
directionality. In other words in each of these nucleic acids, proteins and carbohydrates,
depending on which direction we're adding the monomers we're going to get different
structures and different functions in each of those different molecules. And so like
I said, monomers are the building blocks of polymers. And so over here, the letters, the
analogy is going to be the letters, when you put them together, the monomers eventually
become polymers. And the polymers are made of monomers. In other words we can take monomers,
put them together and then we can have meaning. Now what do I mean by putting them together.
It's not like letters inside us, it's chemicals. Chemicals that are going to be bonded together.
So an example, let me get a pen, an example would be an amino acids. So remember proteins
are made up of amino acids. So here would be first amino acid, amino acid 1, amino acid
2. They're not attached together but we're going to attach them together to build a protein.
And so to attach them together we do what's called dehydration synthesis. And it's going
to be important that you understand dehydration in just a second. So let's look at this amino
acid right here. And this amino acid right here and you can see that we're forming a
bond between the two. But what actually is missing in that bond? Because we have a C
here, so a carbon and we have a nitrogen here. So there's a carbon here and a nitrogen here.
So what's missing when we bond those together? Well we're missing an oxygen and two hydrogens.
And so what are we missing when we attach those together? We're missing water. And so
what happens in dehydration synthesis is that we lose a water and we form a bond. In this
case it's just a covalent bond and more specifically we call that a peptide bond because it's between
two peptides. So we can attach another one on this side, another one on this side, another
one on this side and eventually we have a protein. Now that's how we put sugars together.
That's how we put amino acids together. That's how we put nucleic acids as well as amino
acids together. It's through dehydration synthesis. Now let's say we want to break them apart.
How do we do that? Well let's look. Here's our peptide bond again. How do we break that
apart? Well now we're going to add a water. And so if we add H2O here that's going to
actually break that and now we're going to have monomer 1, monomer 2, those two amino
acids again. And so where do we get the building block of proteins? We get it in our diet.
So when I eat something, let's say I eat a big steak, what happens first, well that goes
through my digestive system where hydrolysis occurs. We break that protein apart into its
amino acids. Then I weave that back together again through a polymer to make a protein.
That's what makes me. So we get that through our diet. So let's go through those four different
macromolecules. Remember nucleic acids, proteins, lipids, carbohydrates. So the first ones are
going to be the nucleic acids. Nucleic acids are the genetic material. And they pass that
on. The two different types are RNA and DNA. And we've talked about those before. But let's
talk about the nucleotides. So nucleotides are going to be the building block of a nucleic
acid. And so what are the three parts of it? Well one part is going to be the phosphate.
So we have a phosphate group. Remember with ATP, you're familiar with what a phosphate
group does. Next we have a five carbon sugar. In the case of DNA it's going to be called
deoxyribose. In RNA it's going to be ribose. So now we've got a phosphate group attached
to a sugar and then we're going to attach to a base. And so the three parts of a nucleic
acid in both RNA and DNA are going to be a phosphate group attached to a sugar attached
to a base. And so if we draw this up here, let's get a place where we can actually see
them, there would be a phosphate here. That would be attached to a sugar here and a phosphate
here and a sugar here. And so the backbone is actually made of this portion right here.
It never changes. It's a phosphate attached to a sugar attached to a phosphate attached
to a sugar. And then what actually goes out here are going to be these things. These are
the nitrogenous bases. These are the letters of RNA or the letters of DNA. Cytosine, guanine,
adenine and uracil in RNA. Cytosine, guanine, adenine and thymine in DNA. The other difference
here is in DNA. We actually have a double helix so those attach together. But the one
thing we haven't talked about is the sidedness or the directionality of nucleic acids. So
if we look here at this one sugar, if I count these off, let me find a color that you can
actually see. This is called the 1 prime carbon right here. This is the 2 prime carbon and
the 3 prime carbon would be right here. This would be the 4 right here and then this would
be the 5 prime, you see that right up here, 5 prime carbon. So what does that mean? If
we're looking at RNA there's going to be a 3 prime end at this end. And that means there's
going to be a 5 prime end on the other side. In other words, RNA flows in one direction
from 3 prime in this case to 5 prime. If we look over here on this side, this would be
the 3 prime end of this strand. That means if we follow it all the way up this would
be the 5 prime stem of this one. Likewise, this one runs in the opposite direction. This
would be the 3 prime end and this would be the 5 prime. And so when you see 3 prime and
5 prime, what does that mean? It's just referring to that sugar. In this case it's deoxyribose
if we're talking about DNA and which carbon it's attached on to. So is DNA parallel? Yes.
But it's also, we sometimes refer to it as antiparallel and what that means is that this
one runs in this direction and this one runs in the opposite direction. It becomes really
important when we start copying our DNA. Okay. Let's go to the next one. Next one's are going
to be called proteins. Proteins are made up of amino acids. And this is myoglobin. It's
one of the first ones that we got the structure of. You can see an alpha helix here. I don't
see any beta plated sheets. A pretty simple kind of protein. What are the building blocks
of proteins? Those are amino acids. And so how many are there? There are 20 amino acids.
Those 20 amino acids make up the proteins that we're made up of. And so we have to get
these 20 essential amino acids in our diet. But let's break down the parts of an amino
acid. What do we got? Well we have a carbon in the middle. We have a hydrogen off one
side. We have a carboxyl group, a functional group, on this side which is a carbon, two
oxygens and hydrogen. And then we have an amino group on this side which is a nitrogen
attached to two hydrogens. And so if you look through everyone of these amino acids, they
all have that. So this would be the carbon here in the middle. This would be our carboxyl
group, our amino group, so everyone of these amino acids has that same part to it. All
of this up here is going to be exactly the same. So what makes every amino acid different
is going to be the side chain. So all the stuff that's hanging off of these are the
r chains. And you can see that we get different chemical characteristics. So these ones are
going to be electrically charged. These are polar side chains. These ones are going to
be hydrophobic. These ones right here would be hydrophilic. And so we're going to have
chemical characteristics depending on what amino acid you are. You don't have to memorize
all of the amino acids but you have to know that that's what gives the structure to proteins.
Because it's amino acid after amino acid after amino acid. And if you think about it, let's
say I'm a hydrophobic amino acid, I'm going to fold myself really far on the inside of
the protein to give it the specific structure. Now it also has directionality just like in
DNA we had a 5 prime and a 3 prime. Well, what are going to be the sides? We're going
to have a carboxyl side and we're going to have an amino side. And so as we hook those
together we're going to have sidedness to a protein or a directionality to that. So
example. When I eat that big steak we have to have two enzymes that break down those
proteins called trypsin and chymotrypsin and they're each going to work on different sides.
And they're going to gobble up that protein until we eventually break it down into its
amino acids, which we can use to make our proteins. Okay, next ones are going to be
the lipids. Lipids give us energy but remember they also make the membranes inside us. Lipids,
these are all different types of lipids, cholesterol, triglycerides. This would be regular fat that
makes ice cream taste so good. Phospholipids, you remember, phospholipids are going to make
up the cell membranes. But if you look through all of these can you see one thing that ties
them together? Well it's this long kind of a jagged line that comes out the end. And
what is that long jagged line? It's a carbon, carbon, carbon, carbon, carbon, carbon, carbon
and then there's going to be hydrogen around the outside. And so you've got hydrogen around
the outside, you've got carbon on the inside and so we call that a hydrocarbon tail. And
so hydrocarbon tails are going to be found in cholesterol, fatty acids, all of these
have hydrocarbon tails. What makes those interesting, well there's a huge amount of energy that
we can release from that, so fat has a large amount of energy. But the other thing that's
important is that makes them non-polar. Since they're non-polar they don't like to grab
onto water. And that's why if you throw fat in water it doesn't mix. Except a phospholipid.
Remember a phospholipid is going to have this non-polar portion back here, and then it's
going to have a polar portion up here. So it's amphipathic. It has this charged portion
which is polar up here and that's going to be what faces the outside of a cell membrane
and then this is going to face the inside. Now another important characteristic of lipids
is are they saturated or unsaturated. What does that mean? Well you can see that a lot
of these, these are simply free fatty acids, are going to be straight. And a lot of these
are going to be bent. And the reason that these are bent is because they have a double
bond. If you get a double bond right here, that's going to cause this to actually bend
on itself. If you are unsaturated that means that you don't have hydrogen all the way down
and so you're going to be bent. If you are saturated, saturated means you're going to
have hydrogen all the way around the outside. It's going to be straight. What's a consequence
of that? Butter is a saturated fat. What does that mean? It's straight and it's going to
be a solid at room temperature. Margarine has had hydrogen added to a normally unsaturated
fat, and that hydrogen if you add it here can straighten it out. So margarine would
normally be just a vegetable oil but adding hydrogen, bubbling hydrogen through it, you
can make it straight. And so what's a trans fat? A trans fat are fats that have been,
hydrogen has been added or just naturally occurs. And so what we're finding is that
trans fats are bad in our diet. It's generally better to have unsaturated fats. It doesn't
lead to heart disease. But I digress. The last one then is going to be carbohydrates.
Carbohydrates give us energy. So all of this, what we talk about as carbs, is giving us
energy. But it also can give us structure as well. So chitin for example in insects
or cellulose is plants is structure. What's the building block then? The building block
is going to be sugar. So glucose is that quintessential sugar. Here's a couple of different types
of glucose, alpha and beta. And it depends on where this hydroxyl group comes off of
this. So this would be a simple monomer, glucose, but you can put it together. So amylose, for
example, is what makes up most of starch found in spaghetti. It's just a glucose attached
to a glucose attached to a glucose. Now directionality, what we talk about in carbohydrates is where
that bond comes off. Does it come off here or does it come off here? And that's going
to give us the structure. So for example amylose might be very linear but glycogen is going
to be, almost, you can have a big glycogen molecule, it's almost spherical in shape.
And so the bonding is important as far a carbohydrates go. So again, building block is going to be
glucose, building block is going to be sugars. How do we put those together? How do we attach
these together? It's going to be that dehydration synthesis. And so those are the four building
blocks of life. Four macromolecules. You should know what they are, what they do, what the
monomers are and I hope that's helpful.
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Biological Molecules

2216 Folder Collection
Cheng-Hong Liu published on November 22, 2014
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