Question

In cellular respiration, \(\mathrm{O}_{2}\) is used as a final receptor of (a) ATP and NADH (b) \(\mathrm{H}\) and e- (c) \(\mathrm{Fe}\) (d) Cytochrome

Short answer

The correct answer is (b) H and e-.

Step-by-step solution

Understand the Process of Cellular Respiration

Cellular respiration is an important biochemical process that occurs in cells to produce ATP, the body’s main source of energy. It involves several stages, including glycolysis, Krebs cycle, electron transport chain and oxidative phosphorylation. During these stages, molecules like glucose are broken down and the energy released is used to form ATP. Throughout the process, several other molecules are involved, including oxygen, hydrogen ions (H), and electrons (e-).

Clarify the Role of Oxygen

Oxygen's primary role in cellular respiration is to serve as the final electron acceptor in the electron transport chain. During this process, electrons are transported across the membrane of the mitochondria, eventually combining with molecules of oxygen to form water.

Identify the Correct Answer

With the understanding of the role of oxygen as the final electron acceptor in the electron transport chain, the correct answer is (b) H and e-, as these elements combine with oxygen at the end of the electron transport chain to form water.

Key concepts

Electron Transport Chain

In cellular respiration, the electron transport chain (ETC) is a vital and dynamic stage that takes place in the mitochondria. It can be thought of as a series of connected proteins embedded in the inner mitochondrial membrane. These proteins work together like a relay team, passing electrons from one protein to the next. This process is called electron transport.

The electrons that enter the electron transport chain originate from molecules like NADH and FADH2, which are produced earlier in cellular respiration. As electrons move through the chain, they release energy. This energy is used to pump hydrogen ions ( H^+ ) across the membrane, creating a gradient known as the proton motive force.

• Electron carriers like NADH and FADH2 donate electrons to the chain.
• The energy released pumps protons across the mitochondrial membrane.
• This creates an electrochemical gradient needed for ATP synthesis.

Oxidative Phosphorylation

Oxidative phosphorylation is the grand finale of cellular respiration. It is the process by which the energy from electrons is finally used to form ATP, the energy currency for cells. Once the electron transport chain has established a gradient of hydrogen ions, oxidative phosphorylation can take place.

This process is facilitated by a protein complex known as ATP synthase, which acts like a tiny generator. The flow of hydrogen ions back across the membrane, down their gradient, spins ATP synthase, enabling it to convert ADP and inorganic phosphate into ATP.

• Occurs after electrons have moved through the electron transport chain.
• ATP synthase uses the proton gradient to synthesize ATP.
• This step produces the majority of ATP in cellular respiration.

Final Electron Acceptor

The final electron acceptor is the unsung hero in the process of cellular respiration. In the electron transport chain, oxygen plays this crucial role. At the end of the chain, electrons are transferred to oxygen, which is essential for the production of water and the continuation of the process.

As electrons combine with oxygen and hydrogen ions, water is formed. Without this step, the electron transport chain would back up, halting the production of ATP because there would be no final destination for the electrons.

• Oxygen is the final electron acceptor in the electron transport chain.
• Combines with electrons and protons to form water, completing the process.
• Essential for preventing electron build-up and maintaining the flow of the electron transport chain.