Question

Contrast the electron transport chain in photosynthesis with the one in cellular respiration by identifying sources of the high-energy electrons for each. In photosynthesis, electrons that travel through the electron transport chain in the thylakoid membrane come from ________. In cellular respiration, molecules of ________ supply some of the electrons that travel through the electron transport chain.

1) Water, Oxygen
2) Carbon dioxide, Glucose
3) NaD⁺H, FADH₂
4) ATP, ADP

Answer 1

The sources of high-energy electrons differ between the electron transport chain in photosynthesis and the one in cellular respiration.

Step-by-step explanation:

The electron transport chain in photosynthesis differs from the one in cellular respiration in the source of high-energy electrons. In photosynthesis, electrons that travel through the electron transport chain in the thylakoid membrane come from water. In cellular respiration, molecules of NADH and FADH2 supply some of the electrons that travel through the electron transport chain. Therefore, the correct answer to complete the statements is: 1) Water, 2) NADH and FADH2.

Detailed comparison reveals that, during photosynthesis, the energy from sunlight is absorbed and used to extract electrons from water molecules. These electrons then pass through the chloroplast electron transport chain, leading to the production of NADPH and the generation of a proton gradient that is used to synthesize ATP in a process known as photophosphorylation.

In contrast, during cellular respiration, NADH and FADH2, produced during glycolysis and the Krebs cycle, donate electrons to the electron transport chain within the mitochondria. As electrons move through the chain, they help create a proton gradient across the inner mitochondrial membrane, which is used to produce ATP through oxidative phosphorylation.