Video Transcript
What is a biological macromolecule? (A) A small molecule made up of one type of element. (B) A large organic compound made up of smaller molecules. (C) A large inorganic molecule made up of at least two elements. Or (D) a small inorganic compound made up of a few different elements.
To help us answer this question, let’s have a closer look at the term in the
question. Macro- is a prefix that means large. This means we can immediately exclude any of the answer choices that mention
biological macromolecules being small molecules.
There are four main types of biological macromolecules: carbohydrates, lipids,
proteins, and nucleic acids. These biological macromolecules are organic molecules. In biology, when we refer to a molecule being organic, it means that the molecule
contains atoms of carbon bonded to atoms of hydrogen. For example, the sugar glucose is an organic molecule. You can see here from the simple diagram of its structure that glucose contains
multiple carbon–hydrogen bonds. We can use this information to rule out the answer choices that define biological
macromolecules as inorganic molecules.
Macromolecules tend to be made up of multiple smaller and sometimes repeating
subunits. For instance, many repeating molecules of glucose can join together to form the
macromolecule starch. Therefore, our correct answer must be option (B). A biological macromolecule is a large organic compound made up of smaller
molecules.
