Kaplan Nursing Entrance Practice Exam

How many ATP molecules are produced in a single turn of the Krebs cycle?

1. 1

2. 2

3. 3

4. 4

The correct answer is: 1

In a single turn of the Krebs cycle, one ATP molecule is produced directly. This ATP is generated through a process called substrate-level phosphorylation, which occurs during the conversion of succinyl-CoA to succinate. While the Krebs cycle itself results in the production of other high-energy electron carriers like NADH and FADH2, which contribute to additional ATP generation in the electron transport chain, the direct output from one cycle specifically yields one ATP molecule. Understanding this single ATP production is critical, as it highlights the cyclical nature of the Krebs cycle in cellular respiration, where energy is harvested in various forms, but the immediate output in terms of ATP from one complete cycle is one unit. This foundational concept helps to clarify how energy content in substrates is transformed during metabolic processes.