What is the primary energy source for cardiac muscle?

What is the primary energy source for cardiac muscle?

• A. Anaerobic glycolysis.
• B. Aerobic cellular respiration using fatty acids, glucose, and other molecules.
• C. Ketone body metabolism.
• D. Phosphagen system.

Answer: (B)

The heart relies on continuous aerobic metabolism to meet its constant energy demand. Its primary fuel under normal, well-oxygenated conditions is fatty acids, because beta-oxidation in mitochondria provides a large and steady supply of ATP. The heart also readily uses glucose and lactate, and can use ketones in certain states, but fatty acids remain the main source for sustained activity. Anaerobic glycolysis would only dominate when oxygen is scarce, producing less ATP and leading to lactate buildup. The phosphagen system (rapid, short-term ATP from creatine phosphate) supplies energy for only a few seconds, not the ongoing work of the heart. Ketone bodies can supplement energy under some conditions, but they are not the default primary fuel in a healthy, oxygen-rich heart.

The heart relies on continuous aerobic metabolism to meet its constant energy demand. Its primary fuel under normal, well-oxygenated conditions is fatty acids, because beta-oxidation in mitochondria provides a large and steady supply of ATP. The heart also readily uses glucose and lactate, and can use ketones in certain states, but fatty acids remain the main source for sustained activity.

Anaerobic glycolysis would only dominate when oxygen is scarce, producing less ATP and leading to lactate buildup. The phosphagen system (rapid, short-term ATP from creatine phosphate) supplies energy for only a few seconds, not the ongoing work of the heart. Ketone bodies can supplement energy under some conditions, but they are not the default primary fuel in a healthy, oxygen-rich heart.