Question

Read the following statements with respect to chemiosmosis:
(a) Splitting of water molecules takes place on the inner side of the thylakoid membrane.
(b) NADP reductase enzyme is located on the stromal side of thylakoid membrane.
(c) Energy is used to pump protons from stroma to lumen.
(d) During photophosphorylation, the pH decrease in the lumen of thylakoid.
Which of the above statement(s) is/are correct?

• A. Only a and b
• B. Only b and c
• C. a, b, c and d
• D. Only c and d

Answer 1

The correct option is C a, b, c and d

Splitting of water molecules takes place in the presence of light, due to the presence of PSII-associated water splitting complex loctaed at the inner side of thylakoid membrane. Also called photolysis of water, this releases protons, electrons and oxygen in the lumen of the thylakoid.
The NADP reductase enzyme is located on the stroma side of the membrane of thylakoid.
The energy available in the electrons is used to pump protons from the matrix across the stroma, storing energy in the form of a trans-membrane electrochemical gradient.
The protons move back across the inner membrane through the enzyme ATP synthase. The electron transport chain moves protons across the thylakoid membrane into the lumen. So, the thylakoid lumen has a much more acidic (lower) pH than the stroma.