Which of the following energy substrates can be metabolized aerobically or anaerobically to produce ATP?

Glycogen is an energy substrate that can be metabolized both aerobically and anaerobically to produce ATP. When glycogen is broken down, it first undergoes glycogenolysis, which releases glucose molecules. This glucose can then enter the glycolytic pathway, where it can be processed to produce ATP. If oxygen is present, the process can continue into aerobic respiration, enhancing ATP production through the Krebs cycle and oxidative phosphorylation. In the absence of oxygen, glycolysis can still occur, resulting in anaerobic metabolism that leads to the production of lactate and a smaller yield of ATP.

This versatility in energy production is crucial for exercise, as it allows the body to efficiently utilize available energy sources depending on the intensity and duration of physical activity. Other substrates like amino acids and triglycerides have different metabolic pathways, with amino acids being primarily used for protein synthesis and as a last resort for energy, while triglycerides mainly contribute to aerobic metabolism. Complete proteins are not typically used as an immediate energy source. Thus, glycogen stands out because of its capability to support energy production through both aerobic and anaerobic systems effectively.