Glycolysis, Gluconeogenesis, And Glycogen Metabolism Practice Test

A 24-year-old medical student decides to run a marathon. After 3 hours of continuous, strenuous exercise, she feels weak and dizzy. Her blood glucose is measured and found to be low. To maintain glucose homeostasis during this period of prolonged exercise, her liver is actively synthesizing glucose from non-carbohydrate precursors. One crucial substrate for this process is lactate, which is produced in her exercising muscles.

A 19-year-old man presents with a lifelong history of exercise intolerance. He reports severe muscle cramps, pain, and weakness within minutes of starting any strenuous physical activity. After a recent attempt to lift heavy weights, his urine appeared dark red. A forearm ischemic exercise test shows a failure of blood lactate levels to rise. A muscle biopsy is performed.