Video Transcript
A diagram of an enzyme and some
substrates is shown. Which substrate will the enzyme
bind to?
This question presents us with a
diagram of an enzyme and four different substrates. In order to choose the correct
substrate that will bind to the enzyme, we need to remember what an enzyme does and
how enzymes and substrates bind to one another.
Our body constantly needs to break
down large molecules into smaller ones or build up large molecules from smaller
ones. But the chemical reactions that
break down or build up these molecules can sometimes be very slow. An enzyme is a biological catalyst
which speeds up the rate of such reactions without being used up. Let us have a look at an
example.
When we eat food, we might ingest
large carbohydrates like starch. Starch is too large to be taken up
by the body cells. Therefore, it has to be broken down
in the digestive system into smaller molecules. To aid in this process, our body
produces amylase, an enzyme which helps to break down starch into smaller
sugars.
The molecules produced in an
enzymatic reaction are called products. And the specific products that the
breakdown of starch produces is a smaller sugar called maltose and a smaller
molecule of starch. To do that, the substrate, in this
case starch, has to bind to amylase in the enzyme’s highly specific active site to
build an enzyme–substrate complex. Every enzyme is very specific about
which substrates it will bind to. So, the substrate, or substrates,
must be complementary to the enzyme’s active site in order to bind correctly.
Now, we need to find a substrate
that is complementary in structure to the enzyme shown in the image provided by the
question, which will allow the substrate and enzyme to fit together correctly. The substrate that will fit our
enzyme best is substrate Z because it has a complementary structure to the active
site of the enzyme presented.
Therefore, the correct answer to
our question is Z.
