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Have you
heard or
seen advertisements
for washing
powders that
claim the powders
contain
enzymes that
can remove
specific stains?
Are the claims
of the manufacturers
true?
Let’s see ...
Our bodies use food to
give us energy. Some
foods, like proteins such as
gelatine and starch, need to
be broken down before our
bodies can use them. The
units, or molecules that make
up proteins and starches
are large, but they again are
made up of smaller units.
This breaking down of the
larger units into smaller ones
is called digestion. Our bodies
use enzymes to burn the
foods (or digest them) for
their energy.
The enzymes which help in
digestion are specialists. An
enzyme which would digest a
protein will not digest starch,
nor would a starch-digesting
enzyme break down proteins.
To see how an enzyme can
break down proteins, and at
the same time see if the
claims of manufacturers
of washing powders are
true, try the following two
experiments:
Hole in the jelly
You will need:
- Two small plastic dishes
- Gelatine
- Agar (you can buy
agar from specialist
shops like Brainwave
or Experilab in
Pretoria, or ask your
teacher to get some)
- An ordinary
washing powder
- A biological
washing powder
Read the instructions on
the packets carefully and
prepare two dishes of clear
jelly, one of gelatine, and the
other of agar.
On each jelly, put a small
pinch of an ordinary powder
detergent, and of a so-called
biological washing powder.
The biological
powder is supposed to contain an enzyme which 'removes difficult
stains like egg, gravy and blood'. These contain proteins.
If this is a true claim, we would expect to find the gelatine (a protein) dissolved away under the 'biological' washing powder, but not under the ordinary powder.
The agar (not a protein) should not be dissolved by either. The jelly might soften a little for many reasons, but do not be misled by this. Look for a great hole in the jelly.
Try this experiment and see what you find. If there is a hole in the gelatine under the biological washing powder,
but not one under the ordinary washing powder,
then the claims of the manufacturer are true.
Get rid of the yolk
You will need:
- Two eggs
- Two glasses
- Biological
washing powder
- Ordinary
washing powder
Boil two standard eggs together, and push two teaspoons
into the yolks so that there is some yolk left on the spoons. You may now eat the rest of the eggs!
Dissolve equal amounts of ordinary and 'biological' detergents in two separate glasses of water, and leave a yolk-stained spoon in each glass. After some time you will see that the spoon in
the ordinary detergent still
has yolk on, but the yolk on
the other spoon has been
digested by the 'biological'
detergent. This will happen
if the 'biological' detergent
really contains enzymes that
break down the proteins in
egg yolk.
Enzymes ...
... are special catalysts in our bodies which allow changes such as a
kind of burning to take place very gently.
Digestive enzymes convert food to simpler substances, but many
other enzymes work in the opposite way, linking simple substances
together to form the more complex ones needed to build up tissue.
Enzymes themselves are made of protein.
Enzymes work best at a particular temperature, which is one of the
reasons why our bodies are kept at constant temperatures.
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