Final answer:
Glucose-6-phosphatase is active, or "on," during a fasted state to promote gluconeogenesis and increase blood glucose levels.
Step-by-step explanation:
The enzyme glucose-6-phosphatase is actively involved in the process of gluconeogenesis, which is the synthesis of glucose from non-carbohydrate sources. In a fasted state, when the body’s glucose levels are low, gluconeogenesis is essential to raise blood sugar levels to provide energy, particularly to the brain and red blood cells that rely heavily on glucose. Hence, in a fasted state, glucose-6-phosphatase is on, catalyzing the removal of a phosphate group from glucose-6-phosphate to produce free glucose, which can then be released into the bloodstream.
Glucose-6-phosphatase is found mainly in the liver and kidneys, and its activity contributes to the maintenance of blood glucose levels during fasting. This enzyme is not directly involved in glycolysis, the process of breaking down glucose for energy, but rather it is crucial in the final steps of gluconeogenesis, ensuring that glucose is available for use by the body when dietary sources are scarce.