Question

In the last stage of cellular respiration, oxidative phosphorylation, all of the reduced electron carriers produced in the previous stages are oxidized by oxygen via the electron transport chain. The energy from this oxidation is stored in a form that is used by most other energy-requiring reactions in cells.

From the following compounds involved in cellular respiration, choose those that are the net inputs and net outputs of oxidative phosphorylation.
Drag each compound to the appropriate bin. If a compound is not involved in oxidative phosphorylation, drag it to the "not input or output" bin. (Note that not all of the inputs and outputs of oxidative phosphorylation are listed.)
a. Net input:
O₂
ADP
NADH
b. Net output:
NAD⁺
ATP
Water
c. Not input or output:
CO₂
Glucose
Coenzyme A
Acetyl CoA
Pyruvate

Answer 1

In oxidative phosphorylation, the net inputs are O₂, ADP, NADH, and the net outputs are NAD⁺, ATP, and H₂O. Compounds not involved include CO₂, Glucose, Coenzyme A, Acetyl CoA, and Pyruvate.

Step-by-step explanation:

The net inputs and outputs of oxidative phosphorylation, which is the final stage of aerobic cellular respiration, can be identified from the compounds involved in cellular respiration.

• Net inputs: Oxygen (O₂), ADP, and NADH are inputs because oxygen is the final electron acceptor in the electron transport chain (ETC), whereas ADP and NADH are required for the production of ATP.
• Net outputs: The outputs of oxidative phosphorylation include NAD⁺, ATP, and Water (H₂O), as NAD⁺ is the oxidized form of NADH, ATP is generated through the process, and water is formed when oxygen accepts electrons and protons at the end of the ETC.
• Not input or output: CO₂, Glucose, Coenzyme A, Acetyl CoA, and Pyruvate are not directly involved in oxidative phosphorylation. These compounds are components of earlier stages of cellular respiration such as glycolysis, the transition reaction, and the Krebs cycle (Citric Acid Cycle).

In summary, oxidative phosphorylation harnesses the redox energy from NADH and FADH₂, produced in glycolysis, the transition reaction, and the Krebs cycle, to generate an electrochemical gradient that is used to produce ATP. Oxygen acts as the final electron acceptor, forming water and regenerating NAD⁺, which are all critical components to maintain the flow of electrons through the ETC.