Which of the following is not one
of the four major groups of biological macromolecules? Lipids, proteins, nucleic acids,
fibers, or carbohydrates.
To answer this question, we first
need to know the meaning of the term biological macromolecule. You may already know that the
prefix bio- means life. All life is made of organic
molecules, which are molecules with carbon-hydrogen bonds. So when we use the term biological
to describe molecules, we’re speaking about organic molecules. The prefix macro- means large. So macromolecules are simply large
molecules usually made up of repeating units of smaller molecules. We can combine all these terms to
form a definition of a biological macromolecule.
A biological macromolecule is a
large organic compound made up of smaller molecules. You may remember that there are
four major groups of biological macromolecules. They are carbohydrates, proteins,
nucleic acids, and lipids. Each of these four groups meets our
definition of a biological macromolecule. That is, they are large compounds
made of smaller molecules containing carbon-hydrogen bonds. Carbohydrates, proteins, and
nucleic acids are made up of smaller repeating units that are identical or similar
in composition. These repeating units are called
monomers. Lipids may have some repeating
units, but they also contain unique nonrepeating molecules.
Now let’s return to our
question. We can see that each of the four
groups of biological macromolecules are given as answer choices. But we’re looking for the answer
choice that is not one of the four major groups of biological macromolecules. The term fiber can refer to any
strong material arranged in thin strands, such as muscle fibers or spider silk. In the context of nutrition, fiber
refers to the indigestible compounds within fruits and vegetables such as
cellulose. Therefore, fiber is not one of the
four major groups of biological macromolecules.