Question

when glucose is limited, which molecule can serve as a fuel source for the brain?
a.) ketone bodies
b.) glycerol
c.) cholesterol
d.) triglycerides

Explanation:

When glucose is limited, ketone bodies (produced from fatty acid breakdown) can cross the blood - brain barrier and be used as an energy source by the brain. Glycerol is mainly used in gluconeogenesis (to make glucose) rather than directly as a brain fuel. Cholesterol is not an energy source for the brain. Triglycerides are storage forms of lipids and need to be broken down first, and their components (like glycerol and fatty acids) have more specific fates as mentioned above.

Answer:

A. Ketone bodies