AP BIO Cellular Respiration Lab

8/3/2019 AP BIO Cellular Respiration Lab

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Norris McMahon

1st Period Biology

10/30/09

Title: The Loss of Oxygen by Cellular Respiration

Introduction:

Cellular respiration is one process that eukaryotic cells use to make energy in the

form of ATP (adenine triphosphate) from organic compounds. There are two types ofcellular respiration, aerobic and anaerobic. Aerobic respiration requires the use of oxygen

to function properly and goes through glycolysis, the Krebs cycle, and the electron

transport chain. On the other hand anaerobic respiration works with the absence of

oxygen or without consuming any oxygen. Also anaerobic respiration, like fermentation,involves only glycolysis.

In anaerobic pathways, respiration tends to take place in the form of fermentation.

Fermentation produces ATP by substrate-level phosphorylation that derives from a steady

supply of NAD. There are two types of fermentation, which are alcohol fermentation andlactic acid fermentation. In alcohol fermentation pyruvate is converted into ethanol and in

lactic acid fermentation, pyruvate is reduced to make lactate from NADH. Alcoholicfermentation is useful in brewing and winemaking when it reacts with yeast. An example

of lactic acid fermentation is in human muscle cells. It helps yield ATP when oxygen is

limited.

Glycolysis is the beginning of cellular respiration, which takes place in thecytosol of a cell. The total pathways of glycolysis consist in 10 steps. The first five steps

are considered the energy investment phases where 2 ATP are being consumed. The

last five are the payoff phases, which yield 4 ATP and 2 NADH. In glycolysis, twoATP are used to phosphorylate the molecules. A net gain of 2 ATP is produced at the end

of glycolysis by substrate- level phosphorylation as well as 2NADH converted fromNAD+ by the oxidation of food. Glycolysis yields a total net gain of 2 ATP, 2 NADH, 2H20, and 2 pyruvate.

Once Glycolysis is done, cellular respiration continues into the mitochondrial

matrix where the Krebs cycle begins. The Krebs cycle uses the pyruvate left over fromglycolysis, which contains most of the chemical energy. Each pyruvate that enters the

mitochondrial matrix yields one molecule of Acetyl CoA. Acetyl CoA is formed through

a process when a multienzyme decarboxylizes, pyruvate oxidizes by the transfer of

electrons to NAD+, and coenzyme A is attached. In the eight steps of the Krebs cycle theacetyl CoA gives off carbon dioxide and later joins with oxaloacete, forming citrate. Each

time the Krebs cycle spins 3 NADH, 1 FADH2, and 1 ATP are produced. Being that for

every glucose molecule, 2 acetyl CoA are produced, the Krebs cycle produces a total of6 NADH, 2 FADH2, 2 ATP, and 4 CO2.

The electron transport chain (ETC) is the final ATP producer of cellular

respiration. Although the previous stages have produced some ATP through substrate-level phosphorylation, a majority is produced in the ETC through oxidative

phosphorylation. Electrons are transferred to the ETC by NADH and FADH from

glycolysis and the Krebs cycle. The NADH in the ETC provides a majority of ATP from

cellular respiration while FADH in the ETC produces two ATP. Adding the two ATP


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from glycolysis, and the two from the Krebs cycle, the total number of ATP produced

from cellular respiration is 36-38, depending on the amount made in the ETC.

In this experiment cellular respiration will be used to see how much carbondioxide is produced in the test tube of each variable.

Hypothesis: I predict that as more time allots, the amount of carbon dioxide will increasein the test tubes containing germinating peas. The independent variable, temperature

( Celsius) affected the dependent variables. The dependent variables are the germinating

vs. non germinating peas and the beads are the control.

Materials:

Six Large trays

Ice

Water

Safety equipment

Six Vials

Six steel washers Marker

100 ml graduated cylinder

Twenty germinating peas

Twenty nongerminating peas

Dry peas

Plastic beads

Paper towels

Cotton balls

Six Pipettes

Six ml of potassium hydroxide Non-absorbent rayon

Six stoppers

Petroleum jelly

Thermometer

Timer

Food coloring

Method: See Attached.

Data:

Initial/ Raw Readings

Contents in Test Tube Initial Reading of

Water(ml)

Final Reading of

Volume(ml)

Peas #1 50 54.5

Peas # 2 50 55.0

Beads #1 50 54.5

Beads # 2 50 55.0

Peas & Beads #1 50 54.5


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Peas & Beads #2 50 55.0

Uncertainty: + .01

Data Processing:

Contents in Test Tube Manipulated Date(ml)

Peas #1 4.5

Peas #2 5.0

Beads #1 4.5

Beads #2 5.0

Peas & Beads #1 4.5

Peas & Beads #2 5.0

Uncertainty: + .01

Final Reading Initial Reading = Manipulated Data

Manipulated Readings # 2

Beads Germinating Peas Peas and Beads

Temp(C) Time(m) Reading Differenc

e

R D Corrected R D C

25 0 .87 N/A .83 N/A N/A .89 N/A N/A

0-5 .88 .01 .79 -.04 -.05 .91 .02 .01

0-10 .88 .00 .76 -.07 -.07 .90 .01 .01

0-15 .88 .00 .73 -.10 -.10 .91 .02 .02

10 0 .80 N/A .85 N/A N/A .84 N/A N/A0-5 .84 .04 .79 -.06 -.10 .87 .03 -.01

0-10 .86 .06 .77 -.08 -.14 .89 .05 -.01

0-15 .86 .06 .74 -.11 -.17 .91 .07 .01

Uncertainty: + .01

Difference (D): Reading at time interval initial at 0 minutes

Corrected (C): Difference of (contents in test tube) Difference of (original contents intube)

Conclusion:

The group I was in for this lab was unable to finish all of the vials at each interval.Due to the fact that my group had blended results from another group, I am unsure as to

whether my hypothesis was supported or not. In part of my results I was able to see my

hypothesis supported and other parts, was unrelated. One example of this disunity would

be if one group maintained a constant temperature and the other groups temperaturewasnt close to the original/set temperature.


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Evaluation:

In this lab there were several possible occurrences of error. One error was thefood coloring. If the food coloring was not applied correctly it would spill out of the

pipette. A second error that possibly affected the results was the ice bath. It is hard to

maintain the ice bath at the same constant temperature, so the data could be affected bythat. Another source of error would be a simple misreading of the measurements and

misinterpreting the directions. Being that there was only a certain amount of time, our

group was hurried and tried to finish. Improvements to this lab could significantly changeyour results. If more time was allowed to do this lab or if the vials were set up precursor

to our arrival to class, my group would not have been rushed and would have been able to

get better readings. If the ice bath used had an easier way of maintaining a constant

temperature, it would provide more accurate results. The final enhancement to this labwould be the clarification of the instructions. At first, it took a while for my group to get

started because we were a bit baffled. However if the directions were more clear, it would

have taken us less time and wouldve given us more time.

Documents

AP BIO Cellular Respiration Lab