Lab 6b - Chloroplasts and Mitochondria Flashcards Preview

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Flashcards in Lab 6b - Chloroplasts and Mitochondria Deck (15)
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What are the 2 colour states of Bromthymol blue and what does each state indicate?

Blue: pH is over 7.6

Yellow: pH is below 6.0


What is indicated by the colour of the solution in the tubes of elodea in light and dark + controls at the start of the experiment?

The solution in the tubes is a yellow shade, this means that the pH must be below 6.0. Since we know that the presence of carbonic acid (dissolved CO2) causes a decrease in pH, we can assume that there is dissolved CO2 in all the tubes at the beginning of the experiment.


Explain the colour change that occurs in test tube w/ a solution of bromthymol blue and Elodea, under light conditions.

The solution turns from a yellow to a blue. This indicates that the pH of the solution has increased. The reason the pH of the solution has increased is because the elodea with both light and CO2 at it's disposal underwent photosynthesis. Since CO2 + H2O exists in equilibrium with Carbonic acid, as the CO2 is used the equilibrium shifts to the left, causing a decrease in the concentration of carbonic acid in solution, which also causes the pH of the solution to increase.

TLDR: Soln from Yellow > Blue, = pH has increased, Why? Bc elodea underwent photosynthesis = used CO2, = equilibrium shift to left = ⬇️ in [carbonic acid], less acid means more basic.


What is Aged Tap Water?

Uncovered 24 hrs to let chlorine ions evaporate


Explain if any colour change should occur in a test tube with a solution of elodea, water, bromthymol blue, and under dark conditions.

There should be no colour change. Since colour change requires a drop in pH which is dependant on a decrease in [H2CO3] and this can only occur if photosynthesis occurs. However with no light available to the elodea, photosynthesis will not occur and therefore the pH of the solution will stay acidic and bromthymol blue indicator in solution will also stay yellow.


What is the purpose of having a) a flask with water, bromthymol blue, dissolved CO2, under light conditions b) a flask with water, bromthymol blue, dissolved CO2, under dark conditions?

Both flask a) and b) act as negative controls. a) and b) both do not contain elodea meaning they should stay yellow thus having no shift in pH. If they did change colour this would indicate some type of contamination such as base contamination and the results for the non-control flasks would no longer be reliable.

Tldr; flasks a & b are negative controls, should stay yellow, if dont theres base contamination, non-control results no longer reliable


What is indicated by the colour of a solution of NaOH, bromthymol blue, yeast and sucrose?

The solution is blue. This is because the dissolved NaOH causes the solution to be basic. This also means that sugar fermentation by the yeast cells has not yet occurred, if it had then the solution would increase in [CO2] which would cause a shift in equilibrium to the right and increase the [H2CO3] causing the solution to become acidic and therefore cause the solution to become yellow.


Why does sucrose have to be mixed with the yeast cells?

In order for Sugar fermentation to occur and produce CO2, the yeast cell needs a food source to break down. This food source is provided by Sucrose. Without this sugar fermentation would not occur and we would not see any change in colour (from the equilibrium of CO2 + H2O shifting right toward H2CO3).


Which gas did the yeast cells produce and how do you know?

The yeast cells produced CO2. We know this because when a yeast has a food source (sucrose), water and has no access to O2 (corked tightly), yeast undergo fermentation. A byproduct of fermentation is CO2, this is supported by the fact that the solution turned yellow; acidic, when it was originally basic due to the dissolved NaOH. An increase in production of CO2 in H2O causing a shift in it's equilibrium to the left increasing [H2CO3] making the solution acidic would explain the solution with yeast turning yellow, and the solution w/o yeast remaining blue.


Where are protons pumped, from and to, during the electron transport chain?

From the inside of the inner mitochondrial membrane to the outside of the inner mitochondrial membrane.


What is Proton-motive force? What does the Proton-motive force do/cause?

The combined effect of concentration gradient and voltage gradient. The Proton-motive force causes H+ back to the inside of the inner mitochondrial membrane, through specialty channels that are a part of ATP synthase. The energy of the proton-motive force is what's used to phosphorylate ADP.


What is the phosphorylation created by the flow of protons through the ATP synthase channels called?

Oxidative phosphorylation


How do you calculate the rate of succinate dehydrogenase?

umoles of succinate to fumerase/oxidized DCIP consumed/reduced DCIP (2) - umoles of succinate to fumerase etc divided by t2-t1 >> umoles2 - umoles1 / t2 - t1.


How do you calculate number of umoles of oxidized DCIP? How do you calculate number of umoles of succinate converted by succinate dehydrogenase to fumarate?

uM of oxidized DCIP x L of total solution (5mL)

umoles of oxidized DCIP consumed (aka reduced DCIP) = umoles of succinate to fumarate via succinate dehydrogenase


During the mitochondrial assay of human cheek cells, FAD is a cofactor required, Where did it come from?

Mitochondrial assay buffer