Video Transcript
Why are enzymes often included in
biological washing powders? (A) Enzymes can reduce the amount
of water needed in a washing machine. (B) Enzymes help prevent the
breakdown of clothing fibers, so clothes last longer. (C) Washing powders with enzymes
smell nicer than washing powders without enzymes. Or (D) enzymes can help break down
and remove stains caused by food.
In this question, we are expected
to apply our knowledge of enzymes to answer the question. Questions that require you to use
your knowledge to solve a problem tend to be a bit trickier than straightforward
recalling of facts. With this question, it’s a good
idea to rule out any answer that does not have anything relevant to the biological
actions of enzymes. To help us to do this, we will
first go over the key facts about enzymes. What is an enzyme and how does it
work?
An enzyme is a biological catalyst
that speeds up the rate of reaction without being used up itself. Catalysts work by lowering the
activation energy needed to start the reaction. Let’s look at a couple of graphs to
help illustrate this. We can see that more activation
energy is required for the reaction to occur on the left, where there is no
enzyme. The activation energy is much lower
on the right in the reaction involving an enzyme.
Now let’s look at how enzymes lower
the activation energy. Each enzyme has an area called an
active site, which is specifically shaped to fit the substrate like a lock and a key
fit together. This is called the lock-and-key
model. First, a substrate molecule binds
to the active site of the enzyme, which forms an enzyme–substrate complex. As the reaction completes, the
enzyme releases the product. Since a bond was broken in this
example, this could be a digestive enzyme.
Digestive enzymes are used for many
different roles in science. Digestion is the breakdown of large
insoluble molecules into small soluble ones. If we look at common biological
macromolecules, we can see the bonds that digestive enzymes can break. In proteins, protease enzymes break
peptide bonds between amino acids. In carbohydrates, carbohydrases
break glycosidic bonds between monosaccharides. And in lipids, lipases break ester
bonds between fatty acids and glycerol. Once digestion is complete, what is
left are amino acids, monosaccharides, glycerol, and fatty acids. All these except for fatty acids
are soluble in water. Fatty acids are soluble in soapy
water.
So, let’s take what we know about
enzymes and apply it to the question. It may not be immediately obvious
which answer is right, but let’s review what we know about enzymes. They help catalyze reactions
without being used up themselves. We have digestive enzymes in our
bodies that digest food by breaking bonds in carbohydrates, lipids, and proteins to
release the subunits, which are small, soluble molecules.
So the answer to the question “Why
are enzymes often included in biological washing powders?” is answer choice (D). Enzymes can help break down and
remove stains caused by food.
