AP BIOLOGY

Detailed explanation-1: -The electron transport chain moves protons across the thylakoid membrane into the lumen (the space inside the thylakoid disk). At the same time, splitting of water adds additional protons into the lumen, and reduction of NADPH removes protons from the stroma (the space outside the thylakoids).

Detailed explanation-2: -The passing of the electron in the first part of the electron transport chain causes protons to be pumped from the stroma to the thylakoid lumen. A concentration gradient formed (with a higher concentration of protons in the thylakoid lumen than in the stroma).

Detailed explanation-3: -During photosynthetic electron transport, protons accumulate at high concentration inside the thylakoid space. The concentration gradient between the inside and outside of the thylakoids is the energy source used by the ATP synthase. Protons pass through a channel of the CF0-CF1 ATP Synthase enzyme.

Detailed explanation-4: -A photon of light hits chlorophyll, causing an electron to be energized. The free electron travels through the electron transport chain, and the energy of the electron is used to pump hydrogen ions into the thylakoid space, transferring the energy into the electrochemical gradient.

Detailed explanation-5: -In these organisms, the respiratory electron transport chain is located in both cytoplasmic and thylakoid membranes; the thylakoid membrane is endowed with a dual-function of photosynthetic and respiratory electron transport [29].