Overall, the brain's energy demand is met by blood supply delivering which two resources?

• A. Oxygen and glucose
• B. Lipids and proteins
• C. Vitamins and minerals
• D. Gases and ions

Answer: (A)

Oxygen and glucose power the brain’s energy needs. The brain uses a lot of energy to keep neurons firing, and almost all of that ATP production depends on oxidative metabolism in mitochondria, which requires a continuous supply of oxygen carried by the blood. Glucose is the primary energy substrate that neurons metabolize to generate ATP, and it reaches the brain through the blood across the blood–brain barrier. When either oxygen or glucose delivery is compromised, brain function deteriorates rapidly.

Other options don’t fit because lipids and proteins aren’t the brain’s immediate energy source under normal conditions (they’re used for membranes and other roles), vitamins and minerals act as cofactors rather than direct energy substrates, and gases and ions aren’t energy supplies.