HESI A2 Biology Practice Test 2025 – Complete Exam Prep Resource

The main steps of aerobic cellular respiration include glycolysis, the Krebs cycle, and the electron transport chain, making the provided answer accurate.

Glycolysis is the initial step of aerobic respiration that occurs in the cytoplasm and involves the breakdown of glucose into pyruvate, resulting in the production of a small amount of ATP and NADH. Following glycolysis, if oxygen is present, the pyruvate enters the mitochondria to undergo the Krebs cycle (also known as the citric acid cycle). In this cycle, further breakdown of the pyruvate occurs, producing carbon dioxide, additional ATP, and electron carriers such as NADH and FADH2.

The final step, the electron transport chain, takes place in the inner mitochondrial membrane. Here, the electrons from NADH and FADH2 are transferred through a series of protein complexes, and as they move through these complexes, energy is released. This energy is used to pump protons across the membrane, creating a gradient that drives ATP synthesis through chemiosmosis. The final electron acceptor in the chain is oxygen, which forms water when it combines with electrons and protons.

The combination of these three steps emphasizes the importance of oxygen in aerobic cellular respiration, distinguishing it from