NEET 2026
- Exam
- NEET
- Year
- 2026
- Subject
- Biology
- Chapter
- Chapter
NEET 2026 · Biology · Chapter
During the light reaction of photosynthesis, the chemiosmotic...
During the light reaction of photosynthesis, the chemiosmotic hypothesis explains the mechanism of ATP synthesis. According to this hypothesis, what directly provides the energy that causes a conformational change in the particle of the ATP synthase enzyme?
Options
- AThe continuous accumulation of protons in the thylakoid lumen due to the photolysis of water.
- BThe breakdown of the proton gradient as protons move from the thylakoid lumen to the stroma.
- CThe transfer of electrons from Photosystem II to Photosystem I through the cytochrome complex.
- DThe active pumping of protons from the stroma to the thylakoid lumen through the channel.
Correct answer
B. The breakdown of the proton gradient as protons move from the thylakoid lumen to the stroma.
Step-by-step solution
According to the chemiosmotic hypothesis, ATP synthesis is linked to the development of a proton gradient across the thylakoid membrane.
The accumulation of protons in the thylakoid lumen creates a proton motive force. However, the energy that directly causes the conformational change in the particle of the ATP synthase enzyme is provided by the breakdown of this proton gradient.
As protons move passively from the higher concentration in the thylakoid lumen to the lower concentration in the stroma through the transmembrane channel of ATP synthase, energy is released. This energy drives the conformational change in the particle, enabling it to synthesize ATP from ADP and inorganic phosphate.
Answer: The breakdown of the proton gradient as protons move from the thylakoid lumen to the stroma.
The accumulation of protons in the thylakoid lumen creates a proton motive force. However, the energy that directly causes the conformational change in the particle of the ATP synthase enzyme is provided by the breakdown of this proton gradient.
As protons move passively from the higher concentration in the thylakoid lumen to the lower concentration in the stroma through the transmembrane channel of ATP synthase, energy is released. This energy drives the conformational change in the particle, enabling it to synthesize ATP from ADP and inorganic phosphate.
Answer: The breakdown of the proton gradient as protons move from the thylakoid lumen to the stroma.