Lab 5 worksheet
Based on the data from the floating disk experiment answer the following questions.
(1 pt) What was the source of CO2 in the photosynthesis experiment?
Na2HCO3
(1 pt) Why did the discs sink when you pulled the vacuum in the syringe?
Pulling the plunger outward created a vacuum of low air pressure in the syringe so that the tiny O2 bubbles or dissolved O2 inside the leaves expanded and emerged into larger bubbles through the nooks and crannies between the leaf cells and out of the leaves.
Once O2 gas is out of the leaf cells, the cells have a higher density than water, so the leaves sink.
When the vacuum is released, the liquid bicarbonate fluid refills the voids.(1 pt) What was your hypothesis for the discs in the light and dark beakers (ie-are the discs going to float or sink?)?
My hypothesis was that discs in the dark beaker or in the light beaker but without Na2CO3 would stay sink, and the discs in the light would float.
This is because the leaves in the dark could not perform photosynthesis without light to produce O2 for buoyancy, and neither could the leaf cells without Na2CO3 that would provide CO2 perform photosynthesis to produce O2. In contrast, the leaf ceels in the light beaker would perform photosynthesis to produce O2 in the discs for buoyancy.
(1 pt) What was happening that made them float? In other words, you are observing the production of what molecule?
O2 gas molecules
(1 pt) Did the disks float in the dark? Why or why not?
No. The leaves in the dark could not perform photosynthesis without light to produce O2 for buoyancy,
(1 pt) What was your hypothesis for how the discs would behave in water instead of sodium bicarbonate?
My hypothesis was that discs without Na2CO3 would stay sunk because. leaf cells without Na2CO3 that would provide CO2 could not perform photosynthesis to produce O2
(1 pt) Do some research and describe what other pigments are found in plant leaves. What is the purpose of these pigments?
Two different chlorophylls of different absorbance wavelengths exist. Chlorophyll A absorbs deep red and deed purple color wavelengths while Chlorophyll B absorbs orange-red and green-blue color wavelengths lights. Different absorbance wavelength allows the leaf to absorb more energy from light for photosynthesis to produce more glucose than omitting out certain wavelengths and only specialize in absorbing one particular wavelength’s energy.
(2 pts) Recreate and submit Table 2 ******************* decide which table we want here.
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Table 2 - Number Of Floating Spinach Discs
Legend: Spinach discs were submerged in Na2CO3 water except noted for dH2O.
Light is with an incandescent light bulb 8 inches above. Dark is in a lab bench drawer.
(3 pts) Graph your spinach data (there should be 3 lines on a single graph labeled light, dark or water). Think carefully about what goes on the x- and y-axes. Be sure to distinguish each data set with a legend and provide a descriptive title for your graph as well.
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Figure 1. Number Of Floating Spinach Discs Of Various Conditions
Caption: Spinach discs were submerged in Na2CO3 water except noted for dH2O.
Light is with an incandescent light bulb 8 inches above. Dark is in a lab bench drawer.
(3 pts) Using your graphs from above in how does light affect photosynthesis? How does water (no bicarbonate) effect photosynthesis?
Yes, light does affect photosynthesis. Water with CO2 also affects photosynthesis. Photosynthesis only works with both light and a source of CO2.
Either removing light or removing the CO2 source (Na2CO3) completely stopped photosynthesis. The first 3 minutes of the dH2O beaker’s floating discs were caused by trapped air bubbles while transferring the discs from the syringe into the beaker, so once the trapped air bubbles escapes at minute 4, there were no photosynthesis to produce O2 gas for buoyancy.
Based on the data from the yeast experiment answer the following questions.
(2pt) What was produced during respiration that resulted in changes to your measured heights after incubation at 37C° and what are some other products of respiration?
Glycolysis produces 2 ATPs during the splitting of glucose into pyruvate.
CO2 was produced during respiration. This is for both anaerobic and aerobic respiration. In anaerobic respiration, the 3-carbon pyruvate (slightly oxidized) was reduced by NADH to become the highly reduced 2-carbon ethanol (yeast) or lactic acid (animal), releasing CO2 and replenishing NAD. For aerobic respiration, CO2 is released in the citric acid cycle.
Other product was ethanol. The respiration in this experiment was not very aerated, so, without aerobic respiration, there should be ethanol produced in the tubes.
(2pt) Explain the purpose of tube #1 above including what you expected for a height change in this tube. Explain your reasoning.
Tube #1 is a negative control group of the experiment. The dH2O alone in tube #1 does not have a sugar source to give glucose to run glycolysis to produce CO2. So, there should be no reaction that this experiment looked to see. So, this is a negative control.
(4pt) Excluding tube #1, make a bar graph with the sugar source on the x-axis and the respiration rate (mm/min) on the y-axis.
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Figure 2. Respiration Rate Of Various Sugar Sources for Yeast Fermentation
Caption: Each reaction tube had an initial mixture of yeast and sugar solution volume of about 10mL. The fermentation respiration ran for 45 minutes.
(2pt) Excluding tube #1, which of the substrate(s) above (in tubes 2-4), based on your measured height changes led to the:
Substrate with the fastest respiration rate (mm/min). Use your data above to explain how you know this.
Fastest is Glucose tube at 0.64 mm/min . Looking at the bar chart, the bar sticks out above others is the Glucose tube. Fructose tube 2 also has nearly as much CO2 production as Glucose.
Substrate with the slowest respiration rate (mm/min). Use your data above to explain how you know this.
Lowest is Starch tube at 0.04 mm/min . Looking at the bar chart, the bar the near the x-axis and is lower than others is the Starch tube.
(4pt) Based on your results:
Is the substrate with the fastest fermentation rate a monosaccharide or disaccharide?
Monosaccharide.
Is this what you expected (in other words do your results for Table 1 agree with your initial prediction in the pre-lab)? Explain why or why not.
Yes, my prediction was that glucose would be the fastest respiration substrate because glucose is the direct substarte for glycolysis. The disaccharides Maltose was slower because it needs to be cleaved to give glucose. The Fructose was also a monosaccharide, but it is not a direct substrate of glycolysis and needed to be converted to glucose by yeast cells, which slowed down the process.
(1pt) Based on outside research what sugar source does baker’s yeast prefer? Does this differ from other types of yeast? Be sure to cite any sources used.
According to Karki, Tika B et al., baker’s yeast prefers maltose as sugar for flavoring (1). This is different from the yeast experiment in our lab which only measures the performance of the yeast by respiration speed.
References
Karki, Tika B et al. “Selection and Characterization of Potential Baker's Yeast from Indigenous Resources of Nepal.” Biotechnology research international vol. 2017 (2017): 1925820. doi:10.1155/2017/1925820
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