Video Transcript
Complete the table to state the
correct enzyme, substrate, and product or products. (A) One equals amino acids, two
equals amylase, three equals lipids. (B) One equals nucleotides, two
equals amylase, three equals lipids. (C) One equals amino acids, two
equals pepsin, three equals lipids. (D) One equals nucleotides, two
equals pepsin, three equals lipids. Or (E) one equals amino acids, two
equals pepsin, three equals carbohydrates.
The table has three columns which,
reading from left to right, are titled enzyme, substrate, and product. Before we look at the specific
cells of the table that we need to fill in, let’s temporarily remove our answer
choices to make room for a quick review of these terms.
You might remember that an enzyme
is a biological catalyst, which is a substance that speeds up the rate of chemical
reactions without being used up. A substrate is the specific
molecule, or combination of molecules, which is complementary in shape to a
particular enzyme’s active site. When a substrate binds to its
complementary enzyme, it forms an enzyme–substrate complex, and the accelerated
reaction can occur. The substrate will then be
converted into products, which are released from the enzyme’s active site.
Although some enzymes help to build
large molecules from smaller subunits, the enzymes given in the table are digestive
enzymes, which break down biological macromolecules into smaller molecules. This is critical because we must
break down our food into a small enough form to be absorbed into the
bloodstream. Only then can the nutrients be
delivered to cells to be used for cellular respiration, growth, and repair. These steps make up the process of
digestion.
Different digestive enzymes break
down the different biological macromolecules we obtain from food. For example, the enzyme given in
the first cell of our table is protease, which breaks down the substrate
protein. Now, pause the video to see if you
can remember what subunits, or monomers, make up proteins. If you said amino acids, you are
correct. So, amino acids are the products of
protein breakdown by protease, and we can go ahead and fill in the cell labeled
number one with the missing term.
The second row of the table gives
us the substrate starch and the product glucose, but the enzyme that facilitates
this reaction is missing. Pause the video and see if you can
remember the enzyme that breaks down starch. Starch is a complex carbohydrate,
so it is broken down by the enzyme amylase, first into maltose and then into glucose
monomers. So, we can fill in the cell labeled
as two with the missing enzyme amylase.
The third row of the table gives us
the enzyme lipase and the products glycerol and fatty acids, but we need to figure
out the missing substrate. Can you remember what
macromolecules are composed of glycerol and fatty acids? Hopefully, you remembered that
lipids, which are the substrates of lipases, are made of a glycerol attached to
chains of fatty acids. We can now fill in the final
missing cell of the table, labeled with a three.
Now, let’s compare the answer
choices to the cells of the table that we filled in. The answer choice that correctly
completes the table is (A). One equals amino acids, two equals
amylase, and three equals lipids.
