Video Transcript
Which molecules from the examples
given are classified as types of lipids?
This question provides us with a
list of biological molecules. Then it asks us to determine which
of these molecules will be considered types of lipids. So first, we’ll recall some facts
about lipids. And then we’ll look at the
structures of the molecules in the list provided, and we’ll use what we know to
determine which of these are lipids. Let’s recall that lipids are
molecules that are insoluble in water. They’re generally composed of
carbon atoms, hydrogen atoms, and few oxygen atoms. And they’re characterized by their
possession of what’s known as a hydrocarbon chain. Here, I’ve drawn simplified
diagrams of each of the biological molecules listed. Can you identify them based on
their structure?
If you said triglyceride, nucleic
acid, phospholipids, cholesterol, and cellulose, then you know your biological
molecules. In order to answer our question,
let’s take note of two things here. First, we’re looking for lipids,
which is a type of biological macromolecule. Well, nucleic acids are their own
category of macromolecule. And cellulose is an example of what
we call a carbohydrate. Our four types of biological
macromolecules are proteins, lipids, nucleic acids, and carbohydrates.
Since nucleic acids and cellulose
belong to other categories, we know that they’re not lipids. The second thing to note here is
that lipids are characterized by the possession of a hydrocarbon chain. We can see hydrocarbon chains in
the triglyceride molecule, the phospholipid molecule, and the cholesterol
molecule.
Nucleic acids are composed of a
phosphate group, a sugar, and a nitrogen-containing base. They do not possess hydrocarbon
chains. And cellulose is made of a
repeating pattern of sugars, also without hydrocarbon chains. Since triglycerides, phospholipids,
and cholesterol possess hydrocarbon chains, we know that they’re classified as types
of lipids.
