True or False. The electron transport chain consists of a series of proteins that are embedded in the inner membrane
The correct answer and explanation is :
True.
The electron transport chain (ETC) consists of a series of proteins embedded in the inner mitochondrial membrane that play a crucial role in cellular respiration. These proteins function to transfer electrons from high-energy carriers, such as NADH and FADH₂, to molecular oxygen while simultaneously pumping protons (H⁺) across the membrane to generate an electrochemical gradient.
How It Works
- Electron Donation: NADH and FADH₂ donate electrons to the ETC. NADH transfers its electrons to Complex I (NADH dehydrogenase), while FADH₂ donates electrons to Complex II (succinate dehydrogenase).
- Electron Transfer: The electrons move through a chain of protein complexes—Complex I, II, III, and IV—via mobile carriers, ubiquinone (Q) and cytochrome c. Each transfer releases energy.
- Proton Pumping: Complexes I, III, and IV use this energy to pump protons from the mitochondrial matrix into the intermembrane space, creating a proton gradient.
- Oxygen as the Final Electron Acceptor: At Complex IV (cytochrome c oxidase), electrons combine with oxygen and protons to form water (H₂O). This prevents a buildup of electrons and ensures the chain keeps running.
- ATP Production: The proton gradient drives ATP synthase, an enzyme that synthesizes ATP by allowing protons to flow back into the mitochondrial matrix. This process, called chemiosmosis, generates the majority of ATP during cellular respiration.
Significance
The electron transport chain is essential for aerobic organisms as it produces up to 34 ATP molecules per glucose molecule, making it the most efficient energy-producing step in cellular respiration. Without the ETC, cells would rely solely on glycolysis, producing far less energy.