Identify the statements that accurately describe how hydrogen ion concentration

Question

Identify the statements that accurately describe how hydrogen ion concentration relates to energy production in oxidative phosphorylation.

1. ATP synthase forms a channel for hydrogen ions to enter the mitochondrial matrix and couples the energy gained from the diffusion of hydrogen ions to the release of ATP.

2. The pH in the intermembrane space is higher than the pH in the mitochondrial matrix.

3. ATP synthase provides energy in the form of ATP to actively transport H into the mitochondrial matrix.

4. Energy is generated as a result of the difference in hydrogen ion concentrationbetween the mitochondrial matrix and the cytoplasm.

5. Hydrogen ions enter the mitochondrial matrix via facilitated diffusion.

6. Hydrogen ion concentration is higher in the intermembrane space than in the mitochondrial matrix.

Explanation / Answer

It depends on what you mean by oxidative phosphorylation. REALLY, the term means the process by which hydrogen ions flow through the ATP synthase to create ATP. However, most textbooks also include the electron transport chain process - I will discuss both here.

Simply put, the electron transport chain is a series of proteins in the inner membrane of the mitochondria. NADH and FADH2 from earlier steps in cellular respiration power the production of ATP. These electron carriers bring electrons to the transport chain and donate the electrons to the embedded proteins. Energy is taken from the electron in the chain to actively pump H+ ions into the intermembrane space against its concentration gradient. Once the electron reaches the end of the chain, it binds to O2 (coming from earlier steps in cellular respiration) to produce water. As H+ ions are pumped into the intermembrane space, a high concentration develops and H+ flows back down its concentration gradient through the ATP synthase protein which functions like a turbine. The spinning of this protein causes the catalysis of ATP production from ADP.

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