Igcse Model Questions Vol1 2023 Biology Question 28

In a fasting adult, the liver releases glucose into the bloodstream at a constant rate of \(2.0\;\text{mmol\,min}^{-1}\). Muscle uptake of glucose is proportional to the blood glucose concentration \([G]\) with a rate constant \(k_{m}=0.5\;\text{L\,min}^{-1}\). Fat tissue also takes up glucose at a constant rate proportional to \([G]\) with \(k_{f}=0.1\;\text{L\,min}^{-1}\). At steady state, the rate of glucose release equals the total rate of uptake.\n\n(a) Calculate the steady‑state blood glucose concentration (mmol\,L\(^{-1}\)) in the fasting state.\n\n(b) After a meal, insulin doubles the muscle uptake constant to \(k_{m}=1.0\;\text{L\,min}^{-1}\) and reduces the hepatic release rate to \(0.5\;\text{mmol\,min}^{-1}\). Fat tissue uptake remains unchanged. Determine the new steady‑state blood glucose concentration.