which below is the correct statement?

Question

a.The BBB displays great permeability to lipid soluble molecules

b. Neurons oxidize most of the substrate they use for energy production

c. Brain produces and utilizes ketones when glucose is scarce

d. After an overnight fast, the brain is deprived of glucose

e. Brain metabolism increases and reduces under resting and exercising conditions, respectively

Answer 1

The correct answer is A.

The blood-brain barrier (BBB) is highly selective, but small lipid-soluble molecules such as oxygen, carbon dioxide, and many lipid-soluble drugs can diffuse across it relatively easily. In contrast, glucose and many other water-soluble molecules require specialized transport proteins to enter the brain.

The other choices are incorrect because:

1. B: Neurons primarily use aerobic metabolism, but this statement is too broad and is not the best answer.
2. C: Ketone bodies are produced by the liver. During prolonged fasting, the brain can utilize ketones but cannot synthesize them.
3. D: After an overnight fast, blood glucose is normally maintained through liver glycogen breakdown and gluconeogenesis, so the brain continues to receive glucose.
4. E: Brain metabolism is relatively stable and does not simply decrease during exercise.