The high maximum reaction rate of glucokinase -the correct answer is b. glucokinase is found in liver and pancreatic cells. it catalyzes the initial step of glycolysis, phosphorylation of glucose to glucose-6-phosphate, which is catalyzed by hexokinase in other tissues. both enzymes are found in the liver. glucokinase has a higher michaelis-menten constant (km) and a higher maximum reaction rate (vmax) than hexokinase; therefore, glucokinase has lower affinity for glucose and a higher capacity to make glucose into glucose-6-phosphate. at low glucose levels, hexokinase, with its higher affinity for glucose, processes glucose to glucose-6-phosphate. at higher glucose levels, hexokinase is overwhelmed (operating at its low vmax) and sufficient substrate is available for glucokinase to process the excess glucose even with its low affinity. glucokinase thus helps to handle large increases in glucose from the gut.answer a is incorrect. the hepatocyte cell membrane is permeable to glucose, which is trapped in the cell after phosphorylation.answer c is incorrect. glucokinase is not inhibited by glucose-6-phosphate. instead, glucokinase action is decreased with decreased insulin and carbohydrate levels.answer d is incorrect. insulin-and glucoserich diets increase glucokinase levels.answer e is incorrect. glucokinase has a relatively high michaelis-menten constant.
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