It is believed that the ratio of cyclic photophosphorylation to noncyclicphotophosphorylation changes in response to metabolic demands. Ineach of the following situations, would you expect the ratio to increase,decrease, or remain unchanged?(a) Chloroplasts carrying out both the Calvin cycle and the reduction ofnitrite (NO2-) to ammonia (This process does not require ATP.)(b) Chloroplasts carrying out not only the Calvin cycle but also extensiveactive transport(c) Chloroplasts using both the Calvin cycle and the C4 pathway

It is believed that the ratio of cyclic photophosphorylation to noncyclicphotophosphorylation changes in response to metabolic demands. Ineach of the following situations, would you expect the ratio to increase,decrease, or remain unchanged?(a) Chloroplasts carrying out both the Calvin cycle and the reduction ofnitrite (NO2-) to ammonia (This process does not require ATP.)(b) Chloroplasts carrying out not only the Calvin cycle but also extensiveactive transport(c) Chloroplasts using both the Calvin cycle and the C4 pathway

Biochemistry

6th Edition

ISBN:9781305577206

Author:Reginald H. Garrett, Charles M. Grisham

Publisher:Reginald H. Garrett, Charles M. Grisham

Chapter21: Photosynthesis

Section: Chapter Questions

Problem 5P: The Relative Efficiency of ATP Synthesis in Noncyclic versus Cyclic Photophosphorylation If...

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In cyclic photophosphorylation, it is estimated that two electrons must be passed through the cycle to pump enough protons to generate one ATP. Assuming that the ΔG for hydrolysis of ATP under conditions existing in the chloroplast is about -50 kJ/mol, what is the corresponding percent efficiency of cyclic photophosphorylation, using light of 700 nm?
It is believed that the ratio of cyclic photophosphorylation to noncyclic photophosphorylation changes in response to metabolic demands. In each of the following situations, would you expect the ratio to increase, decrease, or remain unchanged? (a) Chloroplasts carrying out both the Calvin cycle and the reduction of nitrite (NO2 -) to ammonia (This process does not require ATP.) (b) Chloroplasts carrying out not only the Calvin cycle but also extensive active transport (c) Chloroplasts using both the Calvin cycle and the C4 pathway
. It is believed that the ratio of cyclic photophosphorylation to noncyclic photophosphorylation changes in response to metabolic demands. In each of the following situations, would you expect the ratio to increase, decrease, or remain unchanged? (a) Chloroplasts carrying out both the Calvin cycle and the reduction of nitrite (NO,-) to ammonia (This process does not require ATP.) (b) Chloroplasts carrying out not only the Calvin cyde but also extensive active transport (c) Chloroplasts using both the Calvin cyde and the C, pathway
In cyclic photophosphorylation, it is estimated that two electrons must bepassed through the cycle to pump enough protons to generate one ATP.Assuming that the ∆G for hydrolysis of ATP under conditions existing inthe chloroplast is about -50 kJ/mol, what is the corresponding percent efficiency of cyclic photophosphorylation, using light of 700 nm?
In cyclic photophosphorylation, it is estimated that two electrons must be passed through the cycle to pump enough protons to generate one ATP. Assuming that the AG for hydrolysis of ATP under conditions existing in the chloroplast is about –50 kJ/mol, what is the corresponding percent ef- ficiency of cyclic photophosphorylation, using light of 700 nm?
What is photophosphorylation by oxidative phosphorylation? Explain by comparison.
. It is believed that the ratio of cyclic photophosphorylation to non- cyclic photophosphorylation changes in response to metabolic demands. In each of the following situations, would you expect the ratio to increase, decrease, or remain unchanged? (a) Chloroplasts carrying out both the Calvin cycle and the reduction of nitrite (NO, ) to ammonia (This process does not require ATP.) (b) Chloroplasts carrying out not only the Calvin cycle but also extensive active transport (c) Chloroplasts using both the Calvin cycle and the C, pathway
Thylakoids were isolated from chloroplasts and incubated in the dark in an acidic solution (pH 4) to equilibrate the pH. After 30 minutes, the thylakoids were transferred to a basic solution (pH 8) and kept in the dark. Will this system produce ATP? Explain. Will this system produce G3P? Explain.
Photorespiration is a multienzyme bypass of the Calvin cycle's CO2 fixation process in plants and all other oxygenic phototrophs. This bypass removes and recycles 2-phosphoglycolate, a damaging by- product of photosynthesis in the presence of 02, which is formed when 02 substitutes CO2 in the CO2 fixation pathway. Discuss the situation of fixing 02 (oxygen) rather than CO2 (carbon dioxide) in plants.
a) Draw the carboxylation reaction mechanism catalyzed by Rubisco. Include the substrates, products, key amino acid residues in the active site, and important metal ions. b) Describe each step in the Rubisco carboxylation reaction and why the carbamylated lysine is critical for enzyme activity. c. Describe the purpose of the "regeneration stage" of the Calvin-Benson cycle.
For the chloroplast, the thylakoid membrane separates the thylakoid lumen from the stroma; the protons from the photosystems are transported, like with the mitochondrial inner membrane, against the gradient from the lumen to the stroma. However, the pH(lumen) – pH (stroma) is much larger, about 3.4. Calculate delta psi (the electric potential) for the thylakoid membrane, given that ∆G of proton transport is about the same as for the mitochondrion. Then comment on its permeability to ions, compared to the mitochondrial inner membrane’s permeability to ions.
Daniel Arnon and coworkers carried out experiments with intact, salt- washed chloroplasts to study photophosphorylation. When the chloroplasts were illuminated in the presence of ADP +P, ATP was produced, but oxygen was not produced or nor consumed. ATP formation was not accom- panied by a measurable electron transport involving any external electron donor or acceptor. The overall reaction for this result is: ADP + P -", ATP When NADP+ was included in addition to the ADP + P, ilumination of the intact chloroplats again resulted in resulted in the photophosphorylation of ADP to ATP. In addition, the NADPpt was reduced to NADPH + H* and o, was produced. Moreover, the light-induced reduction of NADP* was greatly decreased if ADP + P; were ommitted. The equation for this reaction is: NADP* + H,0 + ADP + R -", NADPH + H + ATP + }02 Briefly describe the mechanism(s) of these two types of photophosphoryla- tion that explain all of these results.