Glycolysis and gluconeogenesis are opposing pathways in that they begin or end with the same metabolites and share common intermediates and/or enzymes. Yet, for energetic reasons, the two processes cannot be the exact reverse of each other. How is this possible

Due to difference in their products.

Explanation:

Glycolysis and gluconeogenesis are not exact reverse to each other because in glycolysis, glucose is converted into pyruvate, adenosine triphosphate (ATP), NADH, protons i.e. hydrogen ions and water whereas in gluconeogenesis, pyruvate is converted into glucose and glycogen. So due to  the formation of different products of each process we can say that glycolysis is not exact reverse of gluconeogenesis.