Which of the following cells/tissues/organs relies exclusively on glucose to function?

• A. Red blood cells.
• B. White blood cells.
• C. The brain.
• D. Skeletal muscles.

Answer: (A)

Verified step by step guidance

1. Understand the question: The problem is asking which cells, tissues, or organs rely exclusively on glucose as their energy source. This requires knowledge of cellular metabolism and energy utilization in different body systems.
2. Step 1: Recall that red blood cells (RBCs) lack mitochondria. Without mitochondria, RBCs cannot perform oxidative phosphorylation and rely exclusively on anaerobic glycolysis, which uses glucose as the sole energy source.
3. Step 2: Consider white blood cells (WBCs). While WBCs can use glucose for energy, they are not exclusively dependent on glucose. They can also utilize other energy sources like fatty acids under certain conditions.
4. Step 3: Analyze the brain. The brain primarily relies on glucose for energy under normal conditions. However, during prolonged fasting or starvation, it can adapt to use ketone bodies as an alternative energy source, meaning it is not exclusively dependent on glucose.
5. Step 4: Evaluate skeletal muscles. Skeletal muscles can use a variety of energy sources, including glucose, fatty acids, and amino acids, depending on the activity level and metabolic state. Therefore, they are not exclusively reliant on glucose.