Glycolysis, Gluconeogenesis, and PPP (1D) Practice Test

A study of rapidly dividing cells (150–250 words) reported increased demand for ribose-5-phosphate (R5P) for nucleotide synthesis. Investigators observed increased flux through the non-oxidative PPP while NADPH levels remained unchanged. They proposed carbon rearrangement reactions were favored without net oxidation.

Context: non-oxidative PPP interconverts glycolytic intermediates $\leftrightarrow$ R5P

Based on the scenario, which outcome is most consistent with increased non-oxidative PPP flux (with unchanged oxidative PPP)?

A liver perfusion protocol (150–250 words) compared two conditions with equal glucose availability: (i) high ATP/high citrate and (ii) low ATP/high AMP. Investigators monitored the rate of fructose-1,6-bisphosphate formation from fructose-6-phosphate and found it was higher in condition (ii). No changes in enzyme abundance occurred over the time course.

Control point: Fructose-6-phosphate $\xrightarrow{\textit{PFK-1}}$ Fructose-1,6-bisphosphate

Based on the scenario, which regulatory interpretation is most consistent with the observed flux difference?