In humans, the concentration of glucose in the blood ismaintained at roughly 5 mM. Hexokinase (HK II) in muscle is aMichaelis-Menten enzyme and its KM for glucose is about 0.1 mM. Theblood glucose and intracellular glucose concentrations rapidlyequilibrate so that the cellular glucose concentration can beconsidered to be essentially the same as the blood glucoseconcentration. Also, prolonged high concentrations of glucose inthe blood can be toxic.
a) What do the KM and the actual glucose concentration suggestabout the activity of HK II under normal conditions? (In otherwords, how fast is the enzyme going compared to its Vmax?)
b) After a high carbohydrate meal, the blood glucoseconcentration can rise to concentrations much greater than 5 mM.What would be the effect of this concentration change on HK IIactivity in muscle tissue?
c) Given the information and your answer in part b, what wouldbe the net effect on the person’s blood glucose concentration aftera high carbohydrate meal?
