Daniel Arnon and coworkers carried out experiments with intact, salt-washed chloroplasts to study photophosphorylation. When the chloroplastswere illuminated in the presence of ADP +P, ATP was produced, butoxygen was not produced or nor consumed. ATP formation was not accom-panied by a measurable electron transport involving any external electrondonor or acceptor. The overall reaction for this result is:ADP + P -", ATPWhen NADP+ was included in addition to the ADP + P, ilumination of theintact chloroplats again resulted in resulted in the photophosphorylation ofADP to ATP. In addition, the NADPpt was reduced to NADPH + H* and o,was produced. Moreover, the light-induced reduction of NADP* was greatlydecreased if ADP + P; were ommitted. The equation for this reaction is:NADP* + H,0 + ADP + R -", NADPH + H + ATP + }02Briefly describe the mechanism(s) of these two types of photophosphoryla-tion that explain all of these results.

It is given that experiment is conducted by Daniel Arnon and coworkers with salt washed, intact…

Answered: Daniel Arnon and coworkers carried out…

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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The Relative Efficiency of ATP Synthesis in Noncyclic versus Cyclic Photophosphorylation If noncyclic photosynthetic electron transport leads to the translocation of 7 H+/2e- and cyclic photosynthetic electron transport leads to the translocation of 2 H+/e-, what is the relative photosynthetic efficiency of ATP synthesis (expressed as the number of photons absorbed per ATP synthesized) for noncyclic versus cyclic photophosphorylation? (Assume that the CF1CF0-ATP synthase yields 3 ATP/14 H+.)
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?
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.
The coenzyme NADP is the terminal electron acceptor in chloroplasts, according to the reaction 2 H₂O + 2 NADP+ 2 NADPH + 2 H+ + O₂ Calculate the equilibrium constant, K'eq, for this reaction at 25 °C. + Use an E'° of -0.324 V for NADP and 0.816 V for H₂O. K'eq = x10
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.
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
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?
For the following questions, choose one to discuss: chloroplast/photosynthesis State at the outset which one you will discuss. A) What role do proton gradients play in the process of photosynthesis proton gradients allow B) Where are proton gradients formed? Within what structures are they seen in chloroplasts How do the structures help them to maintain a gradient? C) Explain where and how the chloroplast or mitochondria uses passive transport and active transport to complete photosynthesis or cellular respiration.
Identify the chemical basis for ApH and AY across the chloroplast thylakoid membrane by dragging the descriptions to their targets. Be sure to notice that the upper arrow iindicates ApH and the lower arrow indicates ΔΨ. ATP synthase complex H+ N ADP + P₁ Light energy ATP H*N Photosystem I/II- Chloroplast N side Aus PN ApH T + Thylakoid membrane HTp H+p Lumen Stroma P side Proton circuit A B High H concentration Low positive charge High positive charge Low H+ concentration Within the image, identify the types of proton translocation by dragging each label to its target. O XH₂ 2H+ + Z 2 H* ZH₂ O XH₂ Z 2H+ ZH₂ 2H+ C A B Proton pump Redox loop
Provide a simplified schematic presentation of (non-cyclic) photophosphorylation. Clearly indicate the location and direction of electron and proton flow as well as organelle compartments. (You can also draw the Z-scheme but then you have to include ADP phosphorylation).
The net equation for oxidative phosphorylation can be written as 2NADH + 2 H+ + O2 →2 H2O + 2 NAD+. Write an analogous equation for the light reactions of photosynthesis.
The reduction potentials of iron in each of the cytochromes in the electron transport complexesvary from 0.The reduction potentials of iron in each of the cytochromes in the electron transport complexes vary from 0.1 V to 0.39 V. Explain why these different values are necessary for the operation of this process

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