Humber Admissions Practice Test

What sequence best describes the aerobic cycle?

1. Krebs cycle -> ETC -> Glycolysis

2. Glycolysis -> Krebs cycle -> ETC

3. ETC -> Glycolysis -> Krebs cycle

4. Glycolysis -> ETC -> Krebs cycle

The correct answer is: Glycolysis -> Krebs cycle -> ETC

The sequence that best describes the aerobic cycle starts with glycolysis, then proceeds to the Krebs cycle, and concludes with the electron transport chain (ETC). Glycolysis takes place in the cytoplasm and is the initial stage of glucose metabolism, where glucose is broken down into pyruvate, yielding a small amount of ATP and NADH. This step is anaerobic but prepares molecules for aerobic respiration. Following glycolysis, the pyruvate enters the mitochondria, where it's converted into acetyl-CoA and enters the Krebs cycle (also known as the citric acid cycle or TCA cycle). During the Krebs cycle, a series of reactions occurs that further breaks down acetyl-CoA, producing more NADH and FADH2, as well as additional ATP. Lastly, the electrons carried by NADH and FADH2 are transferred to the electron transport chain, which is located in the inner mitochondrial membrane. Here, the electrons move through a series of proteins, enabling the generation of a significant amount of ATP through oxidative phosphorylation. This step also consumes oxygen and produces water as a byproduct. In summary, the aerobic cycle begins with glycolysis, leading to the Krebs cycle, and finishing with the electron transport chain