Which of the following is/are true about where electrons end up?
The last molecule of the ETC in the mitochondrian donates electrons to water and releases oxygen
The last molecule of the ETC in the mitochondrion donates electrons to oxygen and makes water
NADH and FADH2 donates electrons to reactions that make glucose in the calvin cycle
NADPH donates electrons to reactions that make glucose into the calvin cycle
To determine which statement is true about where electrons end up, we need to understand the processes involved in cellular respiration and photosynthesis.
1. The first statement: "The last molecule of the ETC in the mitochondrion donates electrons to water and releases oxygen." This statement is incorrect. In the electron transport chain (ETC) of cellular respiration within the mitochondrion, the electrons are passed through a series of protein complexes, ultimately merging with oxygen and forming water. However, the released oxygen comes from splitting water molecules during the light reactions of photosynthesis, not from the ETC in cellular respiration.
2. The second statement: "The last molecule of the ETC in the mitochondrion donates electrons to oxygen and makes water." This statement is correct. As mentioned above, in cellular respiration, the last molecule of the ETC donates electrons to oxygen, which combines with hydrogen ions to form water.
3. The third statement: "NADH and FADH2 donate electrons to reactions that make glucose in the Calvin cycle." This statement is incorrect. NADH and FADH2 are molecules involved in cellular respiration, not photosynthesis. In cellular respiration, NADH and FADH2 donate their electrons to the electron transport chain where they are used to generate ATP. The Calvin cycle, on the other hand, is a part of photosynthesis and involves the fixation of carbon dioxide to produce glucose.
4. The fourth statement: "NADPH donates electrons to reactions that make glucose in the Calvin cycle." This statement is correct. NADPH is a molecule generated during the light reactions of photosynthesis. It carries high-energy electrons captured from sunlight. In the Calvin cycle, NADPH donates these electrons to reactions that use ATP to convert carbon dioxide into glucose.
In summary, the correct statement about where electrons end up is the second one: "The last molecule of the ETC in the mitochondrion donates electrons to oxygen and makes water."
The correct statement is:
The last molecule of the ETC in the mitochondrion donates electrons to oxygen and makes water.