How are ATP produced during this final stage of respiration?
The correct answer and explanation is :
ATP is produced during the final stage of respiration, oxidative phosphorylation, through the electron transport chain (ETC) and chemiosmosis. This process occurs in the inner mitochondrial membrane, where high-energy electrons from NADH and FADH₂ are transferred through a series of protein complexes, generating a proton gradient that powers ATP synthesis.
Explanation (300 words):
During cellular respiration, ATP production is maximized in the final stage, oxidative phosphorylation, which includes the electron transport chain (ETC) and chemiosmosis. This process occurs in the mitochondria, where NADH and FADH₂, generated from glycolysis and the Krebs cycle, donate electrons to the ETC.
The ETC consists of protein complexes (I-IV) embedded in the inner mitochondrial membrane. As electrons move through these complexes, energy is released, which is used to pump protons (H⁺) from the mitochondrial matrix into the intermembrane space. This creates a proton gradient, also known as the proton motive force.
At the end of the ETC, electrons are transferred to molecular oxygen (O₂), which combines with protons to form water (H₂O). This ensures that the electron flow continues.
The accumulation of protons in the intermembrane space creates a high concentration gradient. To balance this, protons move back into the matrix through ATP synthase, a specialized enzyme. As protons pass through ATP synthase, the enzyme uses the kinetic energy from this movement to convert ADP (adenosine diphosphate) and inorganic phosphate (Pi) into ATP.
This process, called chemiosmosis, is responsible for the majority of ATP generation. Each NADH contributes to the production of about 2.5 ATP, while each FADH₂ generates about 1.5 ATP. In total, oxidative phosphorylation produces approximately 26-28 ATP molecules per glucose molecule.
Thus, ATP is synthesized efficiently in the final stage of respiration through the electron transport chain and chemiosmosis, making oxidative phosphorylation the most significant contributor to cellular energy production.