A biologist studies photophosphorylation in isolated chloroplasts from spinach a

Question

A biologist studies photophosphorylation in isolated chloroplasts from spinach and oxidative phosphorylation in isolated mitochondria from rat liver. He incubates the isolated organelles in a lightly buffered medium containing inorganic phosphate in an air-tight chamber. The chamber is equipped with an oxygen electrode to measure changes in oxygen concentration and a pH electrode to measure changes in pH. After additions of various agents, he samples the medium to measure the ATP content. The agents that he adds include the following:

FCCP— a proton ionophore that dissipates pH gradients

DCMU—an inhibitor that binds to plastoquinone

Succinate—a Krebs cycle substrate

ADP—adenosine diphosphate

Cyanide (CN–)—an inhibitor that binds to cytochrome C

The results of the experiments are shown in the table.

Which explains the results of FCCP in both chloroplasts and mitochondria?

FCCP inhibits the flow of protons through electron transport chains, thereby preventing ATP formation.

FCCP accepts the electrons at the end of the electron transport chains and causes electron transport to stop with no ATP formation.

FCCP uncouples electron transport from ATP formation, thereby allowing maximum changes in oxygen with no ATP formation.

FCCP prevents protons from feeding into electron transport chains, thereby inhibiting ATP formation and oxygen consumption.

FCCP inhibits the flow of protons through electron transport chains, thereby preventing ATP formation.

FCCP accepts the electrons at the end of the electron transport chains and causes electron transport to stop with no ATP formation.

FCCP uncouples electron transport from ATP formation, thereby allowing maximum changes in oxygen with no ATP formation.

FCCP prevents protons from feeding into electron transport chains, thereby inhibiting ATP formation and oxygen consumption.

Isolated O2 Ap[ATP] [Conditions Dark, ADP Light, ADP organelle ChloroplasLight ADP,11 MU Succinate no ADP Succinate Mitochondri Succinate ADP, FCCP Succinate ADP CN- Key to symbols -No change Decrease Maximum Decrease Increase Maximum Increase

Explanation / Answer

Option 3rd is correct. FCCP (p-trifluoromethoxy carbonyl cyanide phenyl hydrazone) is a potent oxidative phosphorylation uncoupler. FCCP increases the proton permeability, and disconnect the electron transport chain from the formation of ATP. As we know proton gradient developed across membrane is required for the synthesis of ATP via oxidative phosphorylation. Since FCCP increases the proton permeability, it disrupts the proton gradient developed across membrane and hence uncouple the oxidative phosphorylation from electron transport chain. Hence FCCP is capable of stimulating oxygen consumption without a concomitant increase in ATP production.

Related Questions

Navigate

• Browse (All)
• Browse A
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.