Which of the following best describes the effect on glucose metabolism when insulin levels rise and then fall sharply?

• A. Glucose uptake by muscle and adipose tissue initially increases, then decreases as insulin levels drop.
• B. Gluconeogenesis in the liver remains suppressed even after insulin levels fall.
• C. Blood glucose levels continuously decrease regardless of insulin fluctuations.
• D. Glycogen breakdown in the liver is inhibited throughout the entire period.

Answer: (A)

Verified step by step guidance

1. Step 1: Understand the role of insulin in glucose metabolism. Insulin is a hormone that promotes glucose uptake by muscle and adipose tissue, stimulates glycogen synthesis in the liver, and suppresses gluconeogenesis (the production of glucose from non-carbohydrate sources).
2. Step 2: Analyze the effect of rising insulin levels. When insulin levels rise, glucose uptake by muscle and adipose tissue increases, glycogen synthesis in the liver is promoted, and gluconeogenesis is suppressed. This leads to a decrease in blood glucose levels.
3. Step 3: Consider the effect of falling insulin levels. As insulin levels drop sharply, glucose uptake by muscle and adipose tissue decreases, glycogen breakdown (glycogenolysis) in the liver may resume, and gluconeogenesis may no longer be suppressed, potentially leading to an increase in blood glucose levels.
4. Step 4: Evaluate the options provided in the problem. Compare each statement to the physiological effects of insulin fluctuations. For example, the statement 'Glucose uptake by muscle and adipose tissue initially increases, then decreases as insulin levels drop' aligns with the known effects of insulin.
5. Step 5: Eliminate incorrect options based on the physiological understanding of insulin. For instance, 'Blood glucose levels continuously decrease regardless of insulin fluctuations' is incorrect because blood glucose levels are influenced by insulin levels, and 'Gluconeogenesis in the liver remains suppressed even after insulin levels fall' is also incorrect because gluconeogenesis resumes when insulin levels drop.