Cell Respiration and Carbohydrate Processes in a Yeast Lab
Abstract:
This is a lab that demonstrates the reactions with yeast and
cell respiration. We tested different carbohydrates to see how much gas it
would emit. We found that the more we increased content of glucose and the less
complex (disaccharide compared to polysaccharide) they were more quickly used
in yeast cell respiration.
Introduction:
Cell respiration is the release of CO2 and energy
from organisms. Cellular respiration can take place in prokaryote and
eukaryotic cells. The process of cell respiration involves glucose and oxygen
to produce CO2 and water and ATP energy. The formula for cellular
respiration is C6H12O6 (s)
+ 6 O2 (g) → 6 CO2 (g) + 6 H2O (l)
+ Energy 36/38(ATP). Chemical energy that is released can be stored and
used by the organism. There are three main steps in cellular respiration.
Glycolysis is when the monosaccharide glucose is split. Glucose which is
originally a six carbon sugar gets broken down into 2 sets of a 3 carbon sugar.
When this occurs there is a reduction reaction and a hydrogen is gained to form
water. 2 pyruvates are also formed, along with NAD+, and 2 ATP. The citric
acid cycle is the next process sometimes it is known as the Kreb’s cycle. The 2
three carbons that were produced in glycolysis gets converted into acetyl Co A
and lose a carbon to co2 in oxidation. The NAD+ also gets converted
into NADH because it attracts hydrogen and electrons and is a good carrier. Then the 2 carbon acetyl Co A molecules are
added to a 4-carbon molecule to produce a 6-carbon compound, which is the
citric acid. This citric acid produced is broken down to from a 4-carbon atom
so that it can be used for the next acetyl CoA molecules. The enzymes of NAD
and FAD work to remove hydrogen atoms and high-energy electrons from the broken
citric acid. These electrons and atoms will move to the next phase, which is
the Electron transport chain (ETC). Two more ATP molecules of energy are
produced finally. The enzymes NADH and FADH in the inner membrane pass the
hydrogen atoms to different protein molecules. They drain the energy slowly
from these hydrogen atoms. Some energy is used to create more ATP. Some hydrogen
protons get pumped into the inner membrane space and don’t proceed to get
transported in a chain like the electrons. In the last step of the chain the
electrons are attracted to the highly negative ½ O2 and hydrogen
thus water is formed. When electrons go thru the chain there is a pH increase
in the matrix. There is also chemosmosis, which is when the pumped over
concentrated hydrogen atoms enter ATP synthase in the membrane and the hydrogen
atoms are used with ADP to create more ATP. This process is called oxidative phosphorylation
because it is powered by oxygen.
Hypothesis:
If there
is more glucose then the rate of the cellular respiration will be higher. The control,
which has sugar, will create gas emissions.
Materials:
·
4 test
tubes
·
Potato
Starch
·
Flour
·
Honey
·
Sugar
·
Salt
·
Yeast
·
Warm Water
·
4 valve
stoppers with a tube and syringe attached
Procedure
1)
Collect
all the supplies and label the test tubes with what substance you are testing
and the control.
2)
For every
test tube measure out 1 gram of the different carbohydrates. Then measure out
35 ml of warm water. 0.1 gram of salt is also needed in each test tube. You
also need 1 gram of yeast.
3)
Add the water
first, but do not add yeast till everything else is in the test tube.
4)
Let it
breath for 5 minutes and then set a baseline on the syringe by pulling it back.
5)
Cap the
test tubes and push the air in to seal it.
6)
Then in
five minutes push the air down gently and let the stopper rise and record the
volume of the gas.
7)
Then in
minutes intervals push the stopper down again and record the volume.
8)
End after
10 minutes.
Results
Time
|
Potato
Starch
|
Flour
|
Sugar
|
Honey
|
0
|
1.6
|
2
|
2
|
1.9
|
5
|
2
|
2
|
2
|
3
|
7
|
2
|
3
|
4.5
|
|
8
|
2
|
5.3
|
5.3
|
|
9
|
2
|
7
|
6.2
|
|
10
|
2
|
8
|
7.6
|
Conclusion:
We made one error in the potato starch test so we don’t have
significant data for that experiment. The seal on the cap kept leaking so gas
wasn’t getting recorded in volume. We had to change caps five times to fix it
and then we just couldn’t record good data. We managed to get two points for
the first five minutes. The second
possible error that could have affected our data is that we added the water
last instead of adding the yeast last. Examining the first two data points of
the potato starch we can tell that it didn’t have a large reaction with the
yeast and the test tube wasn’t as warm as the others, which shows there was
less energy released. We can assume that
the points would probably have followed a similar line to the flour. Flour is a
type of wheat starch is also a polysaccharide. Which means it is harder to
break down in cell respiration and takes longer. Eventually if we left our
experiment for longer the cell respiration might have increased in flour
because of the lack of oxygen, would force the yeast to use it. We thought that honey and sugar would react
because they are both forms of disaccharides. Our hypothesis was correct. The
glucose in the sugar control did end up reacting. However if we also left it there
less energy would be produced because of used supplies. The honey was already
slowing down in the rate of respiration. The test tubes were hot after the
reaction, which means that a lot of heat energy was released along with ATP.
Using forms of different carbohydrates along with the remaining oxygen we were
able to produce that CO2 that we could measure from cell respiration.
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