Modern Experimental Biochemistry

Chemistry

Quiz 9 :

Photoinduced Proton Transport Through Chloroplast Membranes

Quiz 9 :

Photoinduced Proton Transport Through Chloroplast Membranes

Question Type
search
arrow
Why does the pH of the suspension solution decrease daring dark intervals?
Free
Essay
Answer:

Answer:

In this problem, we are asked to explain why the pH of the suspension solution goes down during dark periods.
When chloroplast preparations are brought into the light, we see a shift in pH of the solutions; these plant organelles are the site of photosynthesis, and thus react to the presence or absence of light. The biochemistry separates the production of energy from the production of sugar inside the chloroplasts - energy production requires the light, but sugar production does not.
During the dark periods, the proton pumps in the chloroplast cease functioning; they are no longer breaking down water into protons that can drive the production of adenosine triphopshate (ATP). ATP synthase (the enzyme responsible for the production of ATP) continues to pump protons back across the membrane into the solution around the chloroplast until equilibrium is established. This increase in protons back into the solution drives the pH down.

Tags
Choose question tag
close menu
arrow
Design a flowchart outlining the chloroplast preparation procedure and describe the purpose of each step.
Free
Essay
Answer:

Answer:

In this problem, we are asked to draw a flow chart for the chloroplast preparation steps in this experiment.
The isolation steps require a series of steps, mostly involving centrifugation at various speeds, and then several chemical isolation steps to select just for the chloroplasts.
The flow chart would be as follows: img Thus, chloroplasts can be isolated from leaf extracts.

Tags
Choose question tag
close menu
arrow
Explain the chlorophyll extraction procedure in chemical terms. Why is acetone effective in the extraction? How could the experiment be modified to increase the yield of chlorophyll extraction?
Free
Essay
Answer:

Answer:

In this problem, we are asked to explain chlorophyll extraction in terms of chemistry, explaining why acetone is a better solvent for the extraction, and what steps could be taken to improve the yield in the extraction step.
Chlorophyll, as an organic molecule, is largely non-polar, and therefore is more soluble in non-polar solvents such as acetone; acetone will disrupt the pigment-protein complex as well.
To improve yield, we could combine multiple extractions into a larger starting pool; this would require more starting material (leaves).

Tags
Choose question tag
close menu
arrow
Would you expect the rate of proton uptake in this experiment to be dependent on the wavelength of light used? What wavelength(s) is most effective? Explain.
Essay
Answer:
Tags
Choose question tag
close menu
arrow
Examine Equation E9.2 and answer the following questions. (a) What is the oxidizing agent (acceptor of electrons)? (b) What is the reducing agent (donor of electrons)? (c) What is the source of energy for phosphorylation of ADP?
Essay
Answer:
Tags
Choose question tag
close menu
arrow
Describe other methods for measuring the rate of ATP generation during photophosphorylation.
Essay
Answer:
Tags
Choose question tag
close menu
arrow
Explain the effect, if any, of the redox cofactor on the rate of proton uptake.
Essay
Answer:
Tags
Choose question tag
close menu
arrow
A. student in the lab completes part B of this experiment to measure the chlorophyll content of the chloroplast preparation. The final A 652 of the 80% acetone extract was 0.13. What is the concentration of chlorophyll in mg/mL in the chloroplast preparation?
Essay
Answer:
Tags
Choose question tag
close menu
arrow
Describe methods that could be used to measure extrusion of K + , Mg 2+ , or Ca 2+ from chloroplasts.
Essay
Answer:
Tags
Choose question tag
close menu
arrow
Why is the amount of chlorophyll kept constant in all experiments described here?
Essay
Answer:
Tags
Choose question tag
close menu