In the present work, I investigated the origin of the misconception that glucose is the sole metabolic fuel previously described among Brazilian high school students. The results of a multiple-choice test composed of 24 questions about a broad range of biology subjects were analyzed. The test was part of a contest and was answered by a sample composed of undergraduate students as well as biologists and practicing biology teachers. The majority of the responders had difficulties in recognizing the existence of gluconeogenesis and the possibility of ATP production using other fuels other than carbohydrates. Biology teachers and biologists seemed to either lack the knowledge or present the misconception regarding energy-yielding metabolism found among students. I argue that in both cases, biology teachers are likely to teach metabolism-related subjects in a manner that may contribute to the appearance of the misconception among high school students.