Question

question 8 (1 point)
energy is needed to make atp during oxidative respiration. where in the electron transport chain is this source of energy stored?
○ the release of carbon dioxide
○ the water molecule formed when oxygen accepts electrons.
○ an electrochemical gradient of protons across the inner mitochondrial membrane.
○ in the ubiquinone and cytochrome c

Explanation:

To solve this, we analyze each option:

• "the release of carbon dioxide": Carbon dioxide release is part of earlier stages (like the Krebs cycle) and not related to energy storage in the electron transport chain (ETC) for ATP synthesis.
• "The water molecule formed when oxygen accepts electrons": Water formation is the final step of ETC (oxygen as the final electron acceptor) but does not store energy for ATP synthesis.
• "an electrochemical gradient of protons across the inner mitochondrial membrane": In ETC, electrons move through complexes, pumping protons from the mitochondrial matrix to the intermembrane space, creating a proton (H⁺) electrochemical gradient. This gradient's energy is used by ATP synthase to make ATP.
• "In the ubiquinone and cytochrome C": Ubiquinone and cytochrome c are electron carriers in ETC, not energy storage for ATP synthesis.

So the correct source of energy storage for ATP synthesis in ETC is the proton electrochemical gradient.

Answer:

an electrochemical gradient of protons across the inner mitochondrial membrane.