Video Transcript
A diagram of an enzyme and some
substrates is provided. Which substrate will the enzyme
bind to?
This question asks us to identify
which substrate correctly matches with the enzyme we are given. To answer this correctly, let’s
review the key facts about how enzymes work. Enzymes are biological catalysts,
which means they speed up rates of reactions without being changed or used up
themselves. They may work on just one
substrate, for example, salivary amylase, which digests starch molecules down to the
smaller maltose molecules. Or they may work on more than one
substrate, for example, the ligases, which catalyze the joining of two molecules
together. For this question, we will just
refer to one substrate, as in the diagram.
Enzymes are important, as many
essential reactions occurring within our cells are simply too slow to occur by
themselves. Without enzymes, many basic life
processes would be affected and we would not survive. All enzymes are made of one or more
polypeptide chains, composed of many amino acids held together with peptide
bonds. The order of amino acids along a
chain determines the overall 3D shape of the enzyme due to their interactions with
each other and the environment. This means that each type of enzyme
has its own unique shape.
The active site is a specific
region within this shape, where the substrate will fit. This question is asking
specifically about the binding of a substrate and enzyme. So let’s now recap how this
happens. The enzyme and its substrate must
have complementary shapes to be able to fit together. In other words, they must fit
together like jigsaw puzzle pieces. This means that enzymes will only
operate on very specific substrates. Each enzyme, therefore, only
catalyzes one specific reaction.
Having reviewed some key points
about enzymes, let’s return to our question. In the diagram, the enzyme has a
rectangular shape with a box cut out in the middle, representing the active
site. Since the correct substrate will
need to fit into this active site, it should have a structure that complements this
and fits well. In other words, the substrate
should have a protruding box to fit into this shape.
Therefore, the correct answer to
our question “Which substrate will the enzyme bind to?” is V.
