Yeast Respiration Lab Report

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1. Introduction:
Cellular respiration is a catabolic process in which the cell degrade high energy containing food to law energy containing molecules. Cellular respiration takes mainly place in the mitochondria. Cellular respiration can be either aerobic, anaerobic or facultative. Aerobic cells are cells that cannot survive and grow without the presence of oxygen, whereas anaerobic cells are cells that cannot grow in the presence of oxygen they need a place isolated from oxygen to grow and proliferate, and facultative cells such as yeasts are cells that can grow in the presence and in the absence of oxygen. There are also some microorganisms called microaerophilic that require a small amount of oxygen to grow, these cells cannot grow in the
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Invert the tubes upside down in order to make sure that the straight side of the fermentation tube is full with the solution.
4. Incubate for 15 minutes at 37 degrees.
5. Observe how much the solution was displaced in each tube. This indicates the amount of CO2 formed.

Experiment 7.3 – Use a dye as an indicator of electron transport in yeast:

1. Number the six test tubes and fill them using a dropper with 2 ml of yeast solution (put the finger on the tube that correspond to 1ml).
2. Add 4ml of MgCl2 to the first tube, iodoacetamide to the second, citrate to the third, citrate and iodoacetamine to the forth, formaldehyde to the fifth and distilled water to the sixth.
3. Add 0.5 ml of methylene blue to each tube. Shake the tubes to mix the content.
4. Incubate these tubes for 15 minutes at room temperature and then observe color changes after 15 minutes without shaking.

3. Results:

Experiment 7.1- Examining yeast cells:

In this experiment some of the yeast cells observed under the microscope, a small growth on the surface of the cell that represented a bud that was small and that was fused to the cells’ outer membrane. Other cells represented many growth on their
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This shows that the methylene blue was not reduced because no color change occurred and that the methylene blue did not gain any electron, so it did not function as a substitute for oxygen as the final electron acceptor.
The tube that contained the MgCl2 solution showed a slight color change which means that the methylene blue was slightly reduced.
The reason why there were not reduced is maybe because the enzyme found in yeast which is the dehydrogenase was inhibited; the yeast is therefore incapable of carrying out one or more stages in the transfer of hydrogen to methylene blue in order to be reduced.
The tubes that contained citrate, distilled water and citrate+iodoacetamide, there were a definite change in color. This shows that the methylene blue was reduced by accepting hydrogen atoms so it functioned as the final electron acceptor. The reason why the tube that contained both citrate+ iodoacetamide changed in color is because that citrate bypasses glycolysis and directly enters the Krebs cycle.

5. Pre-lab and Post-lab questions:
a. Pre-lab

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