Question

following ingestion of a large amount of fructose, atp consumption occurs more rapidly than atp production in some cells, and the cytosolic atp concentration of the small intestine and liver fall and then recover whereas those in skeletal muscle are relatively unchanged. further analysis shows all three types of cells express fructose transporters. what mechanism is most likely responsible for these findings?

Answer 1

The difference in ATP concentration changes in various cells after fructose ingestion is due to the liver and small intestine rapidly phosphorylating fructose, leading to ATP consumption and depletion, whereas skeletal muscle stores glycogen and uses it more gradually.

Step-by-step explanation:

The most likely mechanism responsible for the observation that ATP consumption outpaces production in small intestine and liver but not in skeletal muscle after a large ingestion of fructose is due to the specific metabolic pathways active in these tissues. While all three types of cells express fructose transporters, facilitating the entry of fructose into cells via facilitated transport, the liver and small intestine cells have pathways that rapidly phosphorylate and use fructose, while skeletal muscle cells store glycogen and therefore may not immediately use fructose for ATP production.

Ingested fructose is swiftly phosphorylated in liver cells, which results in an initial drop in ATP concentration. However, as the phosphofructokinase enzyme is regulated by ATP levels, a high concentration of ATP inhibits the pathway, which limits further ATP consumption and allows recovery. In contrast, skeletal muscle cells are adept at storing glycogen and do not immediately convert the glycogen back to glucose for energy unless required, such as during intense exercise. Hence, their ATP levels remain relatively constant even after fructose ingestion.