During the process of cellular respiration, oxygen ([tex]\(O_2\)[/tex]) plays a crucial role in the final stage called the electron transport chain. The correct answer is:
C. To accept electrons ([tex]\(e^{-}\)[/tex]) at the end of an electron transport chain and cause water ([tex]\(H_2O\)[/tex]) to form.
Here's a detailed step-by-step explanation of how this works:
1. Glycolysis and the Krebs Cycle: Initially, glucose is broken down during glycolysis into pyruvate, which then enters the mitochondria and is further processed in the Krebs cycle (also known as the citric acid cycle). This leads to the production of electron carriers like NADH and FADH₂.
2. Electron Transport Chain (ETC): These high-energy electron carriers (NADH and FADH₂) then donate electrons to the electron transport chain, which is located on the inner mitochondrial membrane.
3. Electron Transfer: As the electrons pass through a series of proteins in the chain, they lose energy. This energy is used to pump protons ([tex]\(H^+\)[/tex]) across the mitochondrial membrane, creating a gradient.
4. Formation of Water: The electrons eventually reach the end of the electron transport chain, where they are accepted by oxygen ([tex]\(O_2\)[/tex]). This step is crucial because it allows the electron chain to continue to flow. Oxygen, by accepting the electrons, combines with the protons ([tex]\(H^+\)[/tex]) that have been pumped to form water ([tex]\(H_2O\)[/tex]):
[tex]\[
4e^- + 4H^+ + O_2 \rightarrow 2H_2O
\][/tex]
5. ATP Synthesis: The energy from the proton gradient is used by ATP synthase to produce ATP, which is the primary energy currency of the cell.
Without oxygen to accept the electrons at the end of the electron transport chain, the chain would stop, no proton gradient would be created, and ATP production would halt. Thus, oxygen is essential for the generation of ATP in aerobic organisms by accepting electrons and forming water.
