Video Transcript
Enzymes act as catalysts. What does a catalyst do? (A) A catalyst ensures a reaction
never ends. (B) A catalyst always maintains a
constant rate of reaction. (C) A catalyst slows down the rate
of a reaction. (D) A catalyst speeds up the rate
of a reaction. Or (E) a catalyst increases the
number of reactants in a reaction.
Enzymes are globular proteins
because they generally have a round shape and are formed from multiple polypeptide
chains joined together. Within their three-dimensional
protein structure, they have a groove or pocket known as the active site. This is where the reactant or
substrate for a particular chemical reaction combine to the enzyme. We often refer to enzymes as
biological catalysts because they catalyze chemical reactions that take place inside
the body. A good example of a chemical
reaction that’s catalyzed by enzymes would be cellular respiration.
But what do we actually mean by
this word “catalyze”? As this question is asking us, what
does a catalyst do? This graph shows the amount of
product the substance produce during a chemical reaction over time when there’s no
enzyme present. We can see that the reaction
progresses at a constant rate as the product is gradually made. However, when we add an enzyme, we
can see that the product is made much more quickly over the course of the
reaction. In other words, the reaction is
happening at a faster rate when the enzyme is present. This is because catalysts such as
enzymes reduce the amount of energy that’s needed for a reaction to take place,
meaning it can happen much more quickly.
We have therefore demonstrated that
the correct answer to the question is (D), a catalyst speeds up the rate of a
reaction.
