Video Transcript
Steroids are a class of lipids. Which of the following is an
example of a steroid found in the human body? (A) Acetylcholine, (B) cholesterol,
(C) phenol, or (D) carboxylic acid.
Let’s start by reviewing some of
the key terms that have been introduced in this question and go over some examples
of steroids and lipids to answer it correctly.
We are told that steroids are a
class of lipids. Lipids are generally composed of at
least one fatty acid, which is a long carbon–hydrogen chain with a carboxyl group at
one end. Certain lipids, such as
phospholipids, have other functional groups like glycerol and phosphate attached to
their fatty acid chains, which permits them certain useful functions like making up
our cell membranes.
The fatty acid tails of lipids are
hydrophobic, or insoluble in water, due to their long hydrocarbon chains. However, they are soluble in other
nonpolar molecules since, as you might recall, like dissolves like. This means that lipids can dissolve
other lipid compounds, which can be useful in allowing lipid-soluble substances like
certain vitamins or steroid hormones to pass through cell membranes directly into
cells.
Now that we have reviewed some
characteristics of lipids, let’s talk about steroids specifically. We could say that lipids is an
umbrella term that includes the steroid family. The most common type of steroids
are cholesterols. Have you ever heard of the hormone
testosterone? How about estrogen? Steroid hormones, which are
sometimes called steroid derivatives, are synthesized from steroids, specifically
cholesterol. These compounds are tetracyclic,
which means that they contain four ring structures like the one shown here.
Now that we have discussed lipids
and steroids, we are able to correctly answer our question. The answer choice that is an
example of a steroid found in the human body is (B), cholesterol.
