Video Demonstration #1: Liver and Hydrogen Peroxide
A. Submit your answers to the following in writing in class on the due date indicated on
the syllabus to Ms. Korb. If diagrams are necessary in your answers, draw them and bring
them to class.
1. What is an enzyme? Why are they important in the human body?
An enzyme is protein that catalyzes, or speeds up, a chemical reaction.
Enzymes are important in the human body because they prolong life. The reason being is
that without enzymes most chemical reactions in biological cells would occur too slowly
or would lead to different products. A depletion of a single critical enzyme could lead to
another disease. Enzymes are like all catalysts. They work by lowering the activation
energy of a reaction allowing the reaction to proceed quicker. Enzymes can really speed
up reactions by the millions. An enzyme is like any catalyst in that it remains unaltered
by the completed reaction therefore allowing the enzyme to continue to function. In
addition, enzymes do not affect the relative energy between products and reagents, and
they do not affect equilibrium of a reaction.
2. Where are enzymes found in human cell organelles? Why is liver used in this
demonstration?
Enzymes are found in the cellular digestive system in human cell organelles. Lysosomes
and peroxisomes are cell organelles are known as the garbage disposal system of a cell.
Both of these organelles are somewhat spherical. They are bound by a single membrane
that is rich in digestive enzymes. They are also naturally occurring proteins that speed up
biochemical processes. Lysosomes can contain dozens of enzymes for degrading
proteins, nucleic acids, and certain sugars called polysaccharides. The eukaryotic cell
could not house such destructive enzymes if they were not contained in a membranebound system.
The liver is used in this demonstration because it shows a practical use of liver. Our
livers play an important role in our metabolism and other bodily functions. The liver
produces bile. Bile is important for digestion. I also think that liver was used in this
demonstration because in our bodies our liver is full of enzymes that break down the
foods that we eat. When you get a cut and you put hydrogen peroxide on the cut where
ever you put the hydrogen peroxide it produces a white foam. This is just like what was
observed in the video. When we placed a raw piece of liver into a test tube that contained
hydrogen peroxide we can see that a white foam is produced. This reaction between the
liver and the hydrogen peroxide will only take place if the liver is raw. The reason being
is that there is a chemical reaction taking place between the raw liver and the hydrogen
peroxide.
2 H2O2„³2H2O+O2
3. In the video, the labels show the temperature as one thing and the thermometer shows
another temperature as the camera focuses on it. This is due to the camera angle. How is
this important in the process of science? How should a thermometer be read?
This question is important to answer because it is important to read the thermometer
correctly so that the same test can be repeated by others. The angle at which the camera is
focusing on the thermometer is different then the angle at which you and we see. This
shows that a thermometer should be read at the same level as the item is at. The
thermometers temperature should not be taken from a view above but rather from the
same level at which it exists. The camera is looking down from an over head view where
as we are looking at it at eye level.
4. Watch each clip and time the event of the bubbles reaching the mouth of the
Erlenmeyer flask. Is there a difference in the time it take the bubbles to reach the top in
each case?
Yes, there is a difference depending on the temperature of the water as seen in the video.
The warmer the water is the quicker the reaction takes place and vice versa the colder the
water the longer amount of time it takes for the bubbles to form. The reaction happens
very slowly at room temperature. The reaction is speed up in the presence of enzyme.
Cells have these enzymes to break down hydrogen peroxide in the cells because these
enzymes break down the hydrogen peroxide compounds produced by some of the cell's
metabolic reactions especially during the transfer of hydrogen¡¦s from organic
compounds to oxygen. This takes place in the peroxisomes organelles. This set of
reactions can be used to eliminate excess oxygen.
5. When more peroxide is added to the room temperature, raw liver, why does the
reaction proceed again with the same piece of liver in the flask?
Because the oxygen that is in the hydrogen peroxide causes the reaction to process again
with the same piece of raw liver to eliminate (get rid of) the excess oxygen that has just
been added.
6. Why is there no production of bubbles in the cooked liver demonstration? (Why is
there a very small amount of bubble formation actually?)
There is very little reaction to the cooked liver because there is no chemical reaction that
can take place. Once something like the liver is cooked a chemical reaction can not take
place and therefore adding the hydrogen peroxide to the cooked liver does not create a
reaction. Whereas when the raw liver was added to the hydrogen peroxide there was a
chemical reaction that took place. The bubbles that we see in the video represent a
chemical reaction taking place between the hydrogen peroxide and the liver.