The brain relies on its blood supply to provide which two key substances?

• A. Oxygen and glucose
• B. Oxygen and cholesterol
• C. Carbon dioxide and glucose
• D. Nitrogen and oxygen

Answer: (A)

The brain’s high energy needs require a steady flow of nutrients from the blood. The two essential substances delivered are oxygen and glucose. Oxygen fuels ATP production in the mitochondria through aerobic respiration, which powers neuronal activity. Glucose serves as the primary fuel for neurons, supporting glycolysis and oxidative metabolism to sustain rapid signaling and neurotransmission. Because the brain has little stored energy, continuous blood supply is crucial.

Cholesterol is important for cell membranes but isn’t an immediate energy source; carbon dioxide is a waste product produced by metabolism and transported away, not a fuel; nitrogen isn’t used as a brain energy substrate in this context.