During a 24-hour fast with no carbohydrate intake, which process supplies glucose for the body's needs

• A. Converting glycogen into glucose
• B. Breaking down red blood cells
• C. Emulsifying fat
• D. Producing more bile

Answer: (A)

When the body goes without carbohydrate for a day, it first taps stored glycogen in the liver to keep blood glucose steady. This process, glycogenolysis, breaks glycogen down into glucose that can be released into the bloodstream to fuel the brain and other glucose-dependent tissues. The liver can provide this glucose because it has the enzyme glucose-6-phosphatase to convert glucose-6-phosphate into free glucose for circulation; muscles, by contrast, keep their glycogen for their own use and can’t supply glucose to the blood.

The other options don’t create the glucose the body needs: breaking down red blood cells isn’t a glucose source for energy; emulsifying fat and producing bile are digestive processes not about producing glucose. If fasting continues beyond liver glycogen stores, the body then relies more on gluconeogenesis, making glucose from non-carbohydrate sources, but the immediate glucose supply during a 24-hour fast is primarily from converting glycogen into glucose.