In the first step of glycolysis, the enzyme hexokinase uses ATP to transfer a phosphate to glucose to form glucose-6-phosphate. The product continues to be oxidized forming pyryvate in glycolysis and is a precursor to acetyl-CoA for the citric acid cycle. Suppose that a cell has only glucose available for energy and that the activity of hexokinase is suddenly stopped in this cell. Which of the following conditions will occur?

Glycolysis must occur before ATP is produced, regardless of whether it is fermentation or the citric acid cycle that follows. Because hexokinase is involved in this preliminary step, if its activity were stopped, the cell could not continue to produce ATP by either pathway.