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.
