Question Video: Classifying Biological Macromolecules Biology

Which of the following is not one of the four major groups of biological macromolecules? [A] Lipids [B] Proteins [C] Nucleic acids [D] Fibers [E] Carbohydrates

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Video Transcript

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.

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