Which of the following sequences correctly represents the flow of electrons during photosynthesis?

(A)\({\rm{NADPH}}\, \to {{\rm{O}}_{\rm{2}}} \to {\rm{C}}{{\rm{O}}_{\rm{2}}}\)

(B)\({{\rm{H}}_{\rm{2}}}{\rm{O}}\, \to {\rm{NADPH}}\, \to {\rm{Calvin}}\,{\rm{Cycle}}\)

(C)\({{\rm{H}}_{\rm{2}}}{\rm{O}}\, \to {\rm{photosystem}}\,{\rm{I}}\, \to {\rm{photosystem}}\,{\rm{II}}\)

(D)\({\rm{NADPH}}\, \to {\rm{electron transport chain }} \to {{\rm{O}}_{\rm{2}}}\)

Short Answer

Expert verified
  1. The option “\({\rm{NADPH}}\, \to {{\rm{O}}_{\rm{2}}} \to {\rm{C}}{{\rm{O}}_{\rm{2}}}\)” is false.
  2. The option “\({{\rm{H}}_{\rm{2}}}{\rm{O}}\, \to {\rm{NADPH}}\, \to {\rm{Calvin}}\,{\rm{Cycle}}\)” is true.
  3. The option “\({{\rm{H}}_{\rm{2}}}{\rm{O}}\, \to {\rm{photosystem}}\,{\rm{I}}\, \to {\rm{photosystem}}\,{\rm{II}}\)” is false.
  4. The option “\({\rm{NADPH}}\, \to {\rm{electron transport chain }} \to {{\rm{O}}_{\rm{2}}}\)” isfalse.

Step by step solution

01

Flow of electrons during photosynthesis

During photosynthesis, solar radiation splits water molecules to release an electron. The released electron flows to PSII, followed by PSI, from where it goes to NADP+to reduce it to NADPH. NADPH then enters the Calvin cycle.

02

Explanation of option (A)

Photolysis occurs in the light reaction of photosynthesis, during which solar radiation splits the water (H2O) molecule into oxygen molecules, protons, and electrons. The electrons and protons then flow to NADP+and reduce it to NADPH.

Thus, the electrons do not flow from NADPH to oxygen.

Therefore, the given option is false.

03

Explanation of option (B)

PSII picks the electrons released during photolysis. From here, it passes through a series of electron carriers, and then PSI picks it up. The electrons then go to NADP+, which combines with protons to produce NADPH.

NADPH synthesized in light reaction then goes to Calvin cycle, used to synthesize the organic compound.

Thus, theelectrons flow from water to NADPH, from where it flows to the Calvin cycle.

Therefore, the given option is true.

04

Explanation of option (C)

Electrons released during photolysis of water flow toward PSII, from where they flow toward PSI through a series of electron carriers.

Thus, electrons flow from PSII to PSI, not from PSI to PSII.

Therefore, the given option is false.

05

Explanation of option (D)

The splitting of water produces oxygen gas, and the electrons are released to pass through the electron transport chain before giving it to NADP+ to form NADPH.

Thus, electrons flow from the electron transport chain to NADPH, not NADPH to the electron transport chain.

Therefore, the given option is false.

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Most popular questions from this chapter

Based on the data in the scatter plot, estimate the percentage change in dry mass of corn and velvetleaf plants if atmospheric CO2 concentration increased from 390 ppm(current levels) to 800 ppm. (a) What is the estimated dry mass of corn and velvetleaf plants at 390ppm? 800 ppm? (b) To calculate the percentage change in mass for each plant. Subtract the mass at 390 ppm from the mass at 800ppm(change in mass), divide by the mass at 390ppm (initial mass), and multiply by 100. What is the estimated percentage change in dry mass for corn? For velvet leaf? (C) Do these results support the conclusion from the other experiments that C3 plants grow better than C4 plants under increased CO2 concentration? Why or why not?

Which process is most directly driven by light energy?

(A). creation of a pH gradient by pumping protons across the thylakoid membrane.

(B) reduction of NADP+ molecules

(C) transfer of energy from pigment molecule to pigment molecule

(D) ATP synthesis.

The presence of only PSI, not PSII, in the bundle-sheath cells of C4 plants has an effect on O2 concentration. What is that effect, and how might that benefit the plant?

Describe the trends shown by the regression lines in your scatter plot. (a) Compare the relationship between the increasing concentration of CO2 and the dry mass of corn to that for velvetleaf. (b) Considering that velvetleaf is a weed invasive to cornfields, predict how increased CO2 concentration may affect interactions between the two species.

How do the CO2molecules used in photosynthesis reach and enter the chloroplasts inside the leaf cell? (See Concept 7.2)

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