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? a. because not every intermediate or enzyme participates in both pathways, conditions will dictate which pathway is stimulated while the other is inhibited. b. levels of atp will dictate which pathway is operational. c. both pathways make use of substrate cycles.

Option (a), (b) and (c).

Explanation:

Glycolysis may be defined as the process of break down of glucose to generate ATP. Gluconeogenesis may be defined as the generation of glucose from the other carbohydrate source. These two process are not reverse of each other exactly.

The ATP level will determine which pathway is activated. The substrate cycles are used in both guconeogenesis and glycolysis pathway. All the enzymes are not exactly similar and the body's biological condition determines the pathway activation and inhibition.

Thus, the correct options are (a), (b) and (c).

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