Video Transcript
Complete the statements to
correctly describe the composition of biological molecules. (a) A protein is made of many
monomers called blank. (b) Many sugar molecules, like
glucose, join together to form blank. (c) A basic lipid molecule is
formed of one blank and three fatty acids.
Key knowledge required to complete
these statements correctly is the structure of biological molecules, also known as
biological macromolecules. So, let’s review what these
molecules are made of and the patterns in their structure as we go through this
question. The question asks us to describe
the composition of biological molecules. So, we need to describe how the
parts of a biological molecule are put together. The biological molecules of concern
here are three types of large molecules that we require from our food and in our
bodies, and these include carbohydrates, proteins, and lipids. And specifically, we’ll be talking
about fats. These types of molecules are called
polymers.
The word polymer literally means
many parts. And you can see in the diagram here
that carbohydrates can be made of many parts. And typically, they’re many, many
times larger than what we have shown here. The parts can be bonded into a
single chain, as shown here, or they’re branched chain carbohydrates as well. A couple common examples of large
or complex carbohydrates include starch, which is used for energy storage, and
cellulose, a structural component of plant cell walls.
Polymers are made of many parts,
and we call those parts monomers, which literally means one part. The monomer of carbohydrates are
sugars and individual sugars are considered carbohydrates as well. In fact, some other carbohydrates
are made of only two sugars bonded together, such as table sugar or sucrose. So, the number of sugars in a
carbohydrate can range from one to thousands. Protein polymers also have a large
range of sizes, and they bond together to form a single chain. A couple common examples of
proteins that you may have heard of before are the hormone insulin and the
structural protein collagen. The monomer unit of a protein is
called an amino acid, and there’s 20 different kinds of amino acids that we build
our proteins from.
Lipids are a little different, and
while some references don’t consider lipids to be polymers, we will recognize them
as polymers. And while lipids also include more
than just fats, we’ll limit our scope to just fats here. Fats are made of a molecule of
glycerol bonded to three fatty acid chains, which can vary in length and bond
type. The monomer units of fats are
glycerol and the fatty acids that attach to the glycerol. The fatty acids vary in length, and
some of them can even have bends. The combination of the different
fatty acids that attach to a glycerol give the fat its identity.
And it looks like we’re ready to
complete the statements in the question. Statement (a) says, a protein is
made of many monomers called blank. If we look at our table down here,
proteins have a monomer unit called amino acids. Statement (b) says, many sugar
molecules like glucose join together to form blank. And we now have the names of a
couple example sugars in our table, glucose and fructose. So, if we put together many glucose
sugars, we’ll get a larger carbohydrate. Statement (c) says that a basic
lipid molecule is formed of one blank and three fatty acids. Looking at our diagram, we can see
one, two, three fatty acids are connected to one glycerol.
