Biology Video 4 - Structure and Function of Biomolecules
(9)(A) compare the structures and functions of different types of biomolecules, including
carbohydrates, lipids, proteins, and nucleic acids
‘Sup, y’all? It’s Lisa D again. I’m just got a text from my buddy Ray in Port Aransas. He was wondering
what living things are made of. He asked, “Are plants and people and bacteria all made of the same
stuff, or are we all made of different atoms and stuff?” Man, Ray Ray is always asking crazy questions
like that! So y’all wanna hear what I told him?
It’s pretty easy. All living things are made of biomolecules. That’s it. Anything that’s living, any cactus,
any mouse, any germ, even us people are made of biomolecules. Pretty simple. Even simpler, there’s
only four of ‘em. You only have to combine four big molecules to make life. That’s crazy! Do y’all
wanna see what they are? Yeah? Let’s make a chart.
Here’s what the Big Four are – carbohydrates, lipids, proteins, and nucleic acids. Every living thing is
made of the Big Four. But, what are they? Let’s fill in the “Also Known As” part of our chart.
Carbohydrates are carbs. You know, sugars. We’ve written that here. And, let’s do lipids. Lipids are fats
and oils and waxes. Now proteins are, well, proteins. I guess there’s no another way to say that. To
me, nucleic acids are just genes. You know, genetic info. Actually, that’s what the N and the A in DNA
stand for, nucleic acids. See? You learn something new every day.
Now, these are big molecules. I mean biiiiiiigggg molecules. But actually, most of them are actually just
long chains of smaller subunits. They’re polymers. That’s what the word polymer means, “many units.”
It’s Greek. In biology, we have to speak Greek all the time! So, let’s fill in our subunits here for our long
chains. Oh, B T dubs, you can also call subunits monomers if you want to, but it doesn’t matter to me.
Whatever y’all want to do.
So carbs are simple sugars or monosaccharides. That makes sense, right? Complex carbohydrates are
made of simple sugars, and the word “monosaccharide” means “one sugar.”
Now, here’s a hiccup: lipids aren’t actually in a chain. They’re big molecules, but no chain. I’m going to
show you a picture later, but for now, we’ll just put “none.”
Now, proteins are made of amino acids, and I mean a lot of amino acids. Picture a Mardis Gras necklace
that’s like 300 or 500 beads long! Alright? Now, DNA is made up of nucleotides. If you look at the DNA
twisted ladder that we all know, if you look really closely at it, you can tell it’s just of a bunch of
subunits. Those are the nucleotides. So, these are the different building blocks of the Big Four.
But, why do we need these guys? Well, I was telling Ray Ray from Port A, that the way I see it, we need
biomolecules functions in our cells and functions in our bodies. So, let’s look at it for the functions of
our cells.
For carbs, it’s actually kind of interesting. Let’s go to a picture so I can show you better. The plant cell
wall that we all know and love is actually made of sugar. It’s a complex carbohydrate called cellulose.
Let’s include that, OK? Let’s go back to our chart – cellulose. So, if you think about it, every plant cell wall
is made of sugar. So, why don’t branches and leaves taste sweeter? I’ll let you figure that one out.
Alright, for lipids, it’s another cell part. The membrane of our cells is actually made of lipids. Specifically,
it’s called phospholipid. Think about it, every single cell in our body has a skin of oil around it! So why
aren’t we all oily and stuff? Hmmmm….
Now, we need proteins for a very important reason. Some proteins are called enzymes. Enzymes break
down molecules, and they assemble big molecules from smaller parts. They speed up chemical
reactions. Our body actually needs enzymes to break down food. Crazy important.
Finally, there’s nucleic acid—really just DNA if you think about it. Nucleic acids have the instructions to
make all of our cell’s parts, and they tell the cells when to divide. Let’s write that. For us eukaryotic
types, you can find the nucleic acids in the nucleus.
Alright, one last comparison to make. Let’s fill in this bad boy for how our bodies need these big ol’
biomolecules, alright? Starting with carbohydrates. Now, we need sugar for energy. Think “sugar rush,”
OK? So carbs are our bodies’ main source of energy. Let’s write that. We’re gonna look at it as instant
energy. Remember that.
Then there are lipids. Now, we need lipids for energy too, but it’s a different kind of energy. Think longterm storage. I remember it as “lipids – L – long-term.” Let’s write that. We humans don’t want to be fat,
right? But think about a lion. He doesn’t know if there’s gonna be any more zebras for the rest of the
month. So when he has extra energy, he’s gonna store it up as fat in his body, just in case. So
remember, long-term energy storage.
What about proteins? Well, most of our body is actually proteins – hair proteins, skin proteins, muscle
proteins. Even the parts of our body that aren’t proteins themselves are made by protein action. So I’m
gonna put “body structures” here.
Finally, nucleic acids are the instructions for life, right? They’re, like, the molecule for inheritance and
reproducing. It’s the combinations of genes that make the instructions for making a baby. If you want
to know more than that, kids, you’re going to have to ask your parents. But for now, let’s put genes and
reproduction for nucleic acids.
Why don’t we check out some pictures of these biomolecules to understand them a little better? Here
we go. Let’s look at carbohydrates. We’ve got some monosaccharides there, some poly starches, and
they’re all made of a bunch of simple sugars chained together. See that?
Let’s look at a lipid. Now remember, a lipid isn’t actually in a chain. It’s pretty complex-looking, but not
a chain, remember that.
Now proteins. Proteins get big and twisted and crazy, but remember, when you look closely at it, it’s
just a really long chain of amino acids. See?
Finally, here’s good ol’ DNA. You’ve known for a while that DNA is this twisted ladder, right? But have
you ever looked really closely at it? You’ll notice all the little subunits. These are all of the nucleotides.
See?
So, what do y’all think I told Ray Ray from Port Aransas? I told him we are all made of the same stuff.
Every organism, from the tiniest germ to the tallest tree, we’re all made of the Big Four biomolecules –
carbohydrates, lipids, proteins, and nucleic acids. It’s pretty cool if you think about it.
Alright, sports fans, that’s it for me. Until next time, it’s Lisa D saying, “You are what you eat!”