Final answer:
The aerobic pathway (D) is the major source of energy for activities lasting more than 90 seconds, involving glycolysis followed by the Krebs cycle and oxidative phosphorylation in the mitochondria, which are considered the cell's powerhouse due to their role in ATP production.
Step-by-step explanation:
The pathway that is a major source of energy production for activity more than 90 seconds in duration is the D) Aerobic pathway. For activities of such duration, the body relies on energy processes that require oxygen. During aerobic respiration, glucose undergoes glycolysis in the cytoplasm to form pyruvate, which then is transported into the mitochondria for further breakdown. The Krebs cycle (also known as the citric acid cycle) occurs in the mitochondria and produces energy carriers that enter the electron transport chain, leading to a significant production of ATP through oxidative phosphorylation.
Glycolysis can occur either aerobically or anaerobically, but for longer activities, the cells predominantly rely on aerobic glycolysis — a process much more efficient in generating ATP than anaerobic glycolysis. This is because aerobic glycolysis leads to complete glucose breakdown in the presence of oxygen, resulting in a higher yield of ATP. The mitochondria, due to their role in aerobic respiration contributing to the majority of ATP synthesis, are often referred to as the powerhouse of the cell.