In which direction do protons flow during electron transport in mitochondria?

In which direction do protons flow during electron transport in mitochondria?

• A. From the mitochondrial matrix to the intermembrane space
• B. From the cytoplasm into the mitochondrial matrix
• C. From the intermembrane space into the mitochondrial matrix
• D. From the inner membrane to the outer membrane

Answer: (C)

In electron transport within the mitochondria, protons are actively pumped from the mitochondrial matrix into the intermembrane space. This process takes place through the electron transport chain, which is embedded in the inner mitochondrial membrane. As electrons are transferred through the various complexes of the chain, they provide the energy necessary to transport protons from the matrix, against their concentration gradient, into the intermembrane space. This movement of protons creates a proton gradient, also known as the electrochemical gradient, which is critical for ATP synthesis. The protons naturally tend to flow back into the matrix, and this flow is harnessed by ATP synthase to produce ATP, showing how the direction of proton flow is fundamentally from the intermembrane space back into the matrix, rather than the other way around. In summary, protons do not flow from the intermembrane space back into the matrix; rather, they are moved into the intermembrane space, setting the stage for ATP production as they return to the matrix.

In electron transport within the mitochondria, protons are actively pumped from the mitochondrial matrix into the intermembrane space. This process takes place through the electron transport chain, which is embedded in the inner mitochondrial membrane. As electrons are transferred through the various complexes of the chain, they provide the energy necessary to transport protons from the matrix, against their concentration gradient, into the intermembrane space.

This movement of protons creates a proton gradient, also known as the electrochemical gradient, which is critical for ATP synthesis. The protons naturally tend to flow back into the matrix, and this flow is harnessed by ATP synthase to produce ATP, showing how the direction of proton flow is fundamentally from the intermembrane space back into the matrix, rather than the other way around. In summary, protons do not flow from the intermembrane space back into the matrix; rather, they are moved into the intermembrane space, setting the stage for ATP production as they return to the matrix.