Sunday, November 17, 2013

Cellular Respiration Lab

Purpose: The purpose of this lab was to observe the effects of cellular respiration on different carbon dioxide concentrations, study the effects of temperature on cellular respiration, determine whether germinating or non-germinating corn respire, and compare the rates of cellular respiration between germinating and non-germinating seeds.

Introduction:  Celllular respiration is converting the chemical energy of molecules that can be used by organisms. Both plants and animals break down glucose for energy and there is a three step process cellular respiration.the first step is glycolysis which creates two pyruvates for the next step along with a net of two ATP. The pyruvates oxidation is not a huge step but creates acetyl CoA from the pyruvates. This will be fed into the citric acid cycle and generate more ATP as well as Electrons carried to the last step which is oxidative phosphorylation and chemiosmosis by NADH AND FADH2. The final step creates the most ATP in the whole process.

Methods: In the experiment, we measured how different levels of carbon dioxide affected the rate cellular respiration, for ten minutes and in a closed system, on 25 room temperature and 25 chilled germinating corn seeds, 25 non-germinating corn seeds, and 25 glass beads. We began with the germinating corn seeds. We then soaked the same 25 germinating seeds in 4°C water for about 10 minutes.  We then tested non-germinating seeds. Finally, we tested glass beads. Glass can’t perform cellular respiration, as it is non-organic. The fact that glass beads were so similar in size to the corn seeds made it the perfect control group. 

The setup.

Getting a reading from germinated seeds.

Germinated seeds getting cold.


Graphs and Charts:
y= CO2 concentration    x= time (in seconds)
(The blue line is the normal germinating seeds, and the green line is the chilled germinating seeds. The red line is the non-germinating seeds, and the purple line is the glass beads.)

Discussion: The result for the germinating seeds was a positive slope for the whole ten minutes of recording, with a final reading that was roughly 1½ times the starting concentration. This should be expected from seeds that are actively using oxygen to grow and release CO2 as a product. Since non-germinated seeds are dormant seeds, which means that they can’t perform cellular respiration, the result was a slope of nearly zero because they simply weren’t actively trying to grow, which would produce CO2. The result was similar for the cold germinating seeds: a slope of zero for the first 1½ minutes of recording, and then a positive slope for the remaining amount of time. That most likely occurred because the seeds were cooled so far below the optimal temperature that they require to perform cellular respiration, they had to warm back up to room temperature before they could begin cellular respiration. As a result, the CO2 concentration in the chamber filled with cold seeds was very similar to that of the ungerminated seeds.

Conclusion:  temperature did play a large role in the rate of respiration as all the test subjects showed the same correlation. With germinated being the fastest, germinated cold getting slower and non germinated being the slowest. We conclude that lower the temperature had a negative impact on the seeds.

References: N/A


Wednesday, November 6, 2013

Enzyme Catalysis Lab (Part 2D)

Purpose: The purpose of part 2D was to test the cenzyme-catalase. The independent variable tested was time, while the dependent variables was H202 consumed as well as KMno4 used when titrating.

Introduction: Enzymes are proteins that speed up the rate of reactions. In this lab enzymes were used on a substrate. A substrate is a solution whose rate of reaction can be catalysed, or accelerated, by the enzymes. The amount of enzymes and substrate in a solution, along with the amount of time the two are together, determine how much of the substrate is catalysed. In this portion of the lab, time was of the essence when it came to determining the amount of substrate that was decomposed by the enzyme.

Methods: In the experiment we had to determine the rate at which seven different timed trails of 10 mL of 1.5% H2O2 solution decomposed after 1 mL of enzyme-catalase was added. Once the enzyme-catalase was added we started a timer, swirled each solution for the ten seconds, and then let them sit for increasing amounts of time. The amounts of time were 10, 30, 60, 90, 120, 180, and 360 seconds. Once time was up we stopped the reactions by adding 10 mL of H2SO4. We then took 5 mL samples from each trial and titrated each one and recorded the amount of KMnO2 used to titrate the 5 mL samples.     


Graphs and Charts:

Discussion: Both the amount of KMnO4 consumed and the amount of water used started at 2.5 milliliters and ended at the same amount. Between the different cups and the amounts of time for which they were exposed to catalase, the two figures-- KMnO4 consumption and H2O use-- seem to decrease and increase in a wave-like pattern. One will decrease while the other increases proportionately, and at some point they each reach a maximum distance from their starting value and begin to move in the other direction-- one increases while the other decreases. It's normal for the KMnO4 amounts to be opposed in this way to the H2O2 amounts, but under normal circumstances, the H2O2 amounts would not decrease after increasing.

Conclusion: our question was to find out the effiency if the enzyme catalase as time being a variable that is changed. We found out that in the fist few tests that our data supported that the enzyme sped up the reaction. However as time got longer we had varied results with our time and it did not support the claim. Errors that may occur is the measurements of our substances and also the time measured might be a little off. Overall we found that most of our data was somewhat accurate.

References: N/A