MCAT Mnemonics: Enzyme Classifications

Ken Tao is the MedSchoolCoach expert on MCAT, and will discuss the different enzyme classifications and what each classification does, including oxioreductase, transferase, hydrolase, isomerase, ligase, and lyase – and how “Over the HILL” will help you remember them.

Full Transcription

Hey everyone. Welcome back to another episode of MCAT Mnemonic Monday. And Ken and I’m an MCAT expert with MedSchoolCoach. Today, we’ve got another biochemistry mnemonic for you on enzyme classifications.

When you start taking practice exams, you’ll find that a lot of passages on exam cover specific enzymes. And you often get questions along the lines of: The enzyme described in the passage is what type of enzyme? And you’ll find that in a lot of those questions, these are your answer choices. So what you need to know is, first of all, these different enzyme classifications and what each classification does.

So first we have oxioreductase. These enzymes are important for redox reactions. They catalyze the reduction or oxidation of different compounds.

Next, we have transferase enzymes. These enzymes transfer groups from one molecule to another. A very common example are kinases. Kinases will transfer phosphate groups from one molecule to another.

Next, we have hydrolase. Hydrolase enzymes catalyze hydrolysis. Hydrolysis means literally: break using water. So here, these enzymes will break chemical bonds using water.

Isomerases are enzymes that catalyze I isomerization reactions so they will convert one molecule from one type of isomer to another type of isomer.

Ligases. You can think of DNA ligase. These enzymes will link two molecules together using a condensation reaction where water is produced as a product.

And finally, we have lyase. Lyase enzymes will also be able to break bonds and form bonds, but they do so without requiring water or oxidation reduction reactions.

OK, so these are different enzyme classifications and our mnemonic for memorizing them is: Over the HILL. Here you can pay attention to the capitalized letters.

So you can see that “O” is for oxioreductase, “T” is for transferase, HILL – H I L L, is for hydrolase, isomerase, ligase, and lyase.

So this is a mnemonic for memorizing the different types of enzymes for the MCAT.