Question Video: A Brief Definition of Enzymes Biology

Which of the following statements correctly defines an enzyme? [A] An enzyme is a product of digestion. [B] An enzyme is a molecule that has been broken-down. [C] An enzyme is a biological catalyst. [D] An enzyme is an inorganic catalyst. [E] An enzyme is a fast reaction.

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Video Transcript

Which of the following statements correctly defines an enzyme? (A) An enzyme is a product of digestion. (B) An enzyme is a molecule that has been broken down. (C) An enzyme is a biological catalyst. (D) An enzyme is an inorganic catalyst. (E) An enzyme is a fast reaction.

Key knowledge required to select the correct solution option is knowing what enzymes are and what they do. Let’s review by taking a look at the enzyme ATP synthase while we review key terms in the question. Like all enzymes, ATP synthase catalyzes or speeds up a chemical reaction. And that makes it a catalyst. Here’s the reaction that ATP synthase catalyzes. ADP plus a phosphate groups yields ATP. The two parts of a chemical reaction that you’re probably used to seeing are reactant or reactants that are converted through the chemical reaction into a product or products. But during a reaction with an enzyme, we say that the substrate or substrates are converted into products or a product. So that means we know that a product is a chemical that’s made in a reaction.

Now let’s take a look at what ATP synthase is gonna do with the substrates, ADP and a phosphate group. The substrates bond to the active site of the enzyme. And that’s where the chemical reaction takes place, forming the product ATP. And the active site of the enzyme is now free to catalyze more reactions. Okay, just a few key terms left. Let’s take a look at “broken down.” If we have a larger molecule that we separate into smaller parts, we say we’re breaking it down. If we go in the opposite direction, we take some smaller molecules and put them together into a larger molecule, we call that building up.

And, of course, the term biological means “from a living system.” And enzymes are proteins produced in living systems. And since proteins are organic molecules, we know that enzymes are not inorganic. And we’re ready to answer our question. Which of the following correctly defines an enzyme? Let’s start with option (A). An enzyme is a product of digestion. Well, we saw that enzymes are catalysts. They’re not products, so option (A) can’t be correct. Option (B) says an enzyme is a molecule that has been broken down, but we saw that enzymes are not broken down. They have to stay intact because they’re reused over and over and over again.

Option (C) says an enzyme is a biological catalyst, and that sounds pretty good. Option (D), an enzyme is an inorganic catalyst, but we already know that can’t be true because proteins are not inorganic. Option (E) says an enzyme is a fast reaction, but we know that enzymes speed up or catalyze chemical reactions. They’re not the reactions themselves. So option (E) is also incorrect. Therefore, option (C), an enzyme is a biological catalyst, is the answer to our question.

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