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Question Video: Describing the Role of Chemiosmosis in Cellular Respiration Biology

Which of the following best describes the role of chemiosmosis in oxidative phosphorylation? [A] Chemiosmosis is the movement of electrons down their electrochemical gradient, which generates energy in the electron transport chain. [B] Chemiosmosis is the chemical breakdown of ATP into ADP and inorganic phosphate. [C] Chemiosmosis is the movement of chemicals dissolved in water down their concentration gradient, across the mitochondrial membrane. [D] Chemiosmosis is the chemical breakdown of water into hydrogen and oxygen ions at the final stage of the electron transport chain. [E] Chemiosmosis is the movement of ions down their electrochemical gradient, which generates ATP.

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Video Transcript

Which of the following best describes the role of chemiosmosis in oxidative phosphorylation? (A) Chemiosmosis is the movement of electrons down their electrochemical gradient, which generates energy in the electron transport chain. (B) Chemiosmosis is the chemical breakdown of ATP into ADP and inorganic phosphate. (C) Chemiosmosis is the movement of chemicals dissolved in water down their concentration gradient, across the mitochondrial membrane. (D) Chemiosmosis is the chemical breakdown of water into hydrogen and oxygen ions at the final stage of the electron transport chain. Or (E) chemiosmosis is the movement of ions down their electrochemical gradient, which generates ATP.

Let’s remove the answer options for now so we can have a look at oxidative phosphorylation and the role of chemiosmosis.

Oxidative phosphorylation is the final stage of aerobic respiration, and it takes place in the inner mitochondrial matrix of eukaryotic cells. In the inner mitochondrial matrix is a collection of proteins, enzymes, proton pumps, and electron carriers that make up the electron transport chain. Electrons donated by coenzymes move through the electron transport chain, releasing energy as they do so. This energy is used by proton pumps to actively transport hydrogen ions from the mitochondrial matrix and into the intermembrane space. These hydrogen ions accumulate in relatively high concentrations in the intermembrane space. They then move down their electrochemical gradient from an area of high concentration to an area of low concentration.

However, these hydrogen ions do not simply move through the membrane but instead move through the channel of ATP synthase. The movement of ions down their electrochemical gradient is called chemiosmosis. The enzyme ATP synthase couples the movement of hydrogen ions with the phosphorylation of ADP, which creates ATP. ATP is an energy-carrying molecule, which is crucial in supporting a wide range of cellular reactions.

Let’s use what we now know about chemiosmosis to answer this question. We now know that chemiosmosis is the movement of ions down their electrochemical gradient. We also know that this movement of ions is coupled to the production of ATP by ATP synthase. So our answer must be option (E). In oxidative phosphorylation, chemiosmosis is the movement of ions down their electrochemical gradient, which generates ATP.

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