In humans, the concentration of glucose in the blood is maintained at roughly 5 mM. Hexokinase...

In humans, the concentration of glucose in the blood is maintained at roughly 5 mM. Hexokinase (HK II) in muscle is a Michaelis-Menten enzyme and its KM for glucose is about 0.1 mM. The blood glucose and intracellular glucose concentrations rapidly equilibrate so that the cellular glucose concentration can be considered to be essentially the same as the blood glucose concentration. Also, prolonged high concentrations of glucose in the blood can be toxic.

a) What do the KM and the actual glucose concentration suggest about the activity of HK II under normal conditions? (In other words, how fast is the enzyme going compared to its Vmax?)

b) After a high carbohydrate meal, the blood glucose concentration can rise to concentrations much greater than 5 mM. What would be the effect of this concentration change on HK II activity in muscle tissue?

c) Given the information and your answer in part b, what would be the net effect on the person’s blood glucose concentration after a high carbohydrate meal?

Expert Solution

a) What do the KM and the actual glucose concentration suggest about the activity of HK II under normal conditions? (In other words, how fast is the enzyme going compared to its Vmax?)

UNDER NORMAL CONDITIONS Km VALUE AND BLOOD GLUCOSE CONCENTRATION (GLUCOSE CONC IS 50 TIMES HIGHER THAN Km) SUGGEST THAT ENZYME ACTIVITY IS NEAR THE Vmax BUT HAS NOT ACHIEVED Vmax. WHEN V=Vmax THEN

Vmax=Vmax S/(Km+S)

1=S/(Km+S)

S/Km+1=1,

S/Km=0

Km=S/0 INFINITY

b) After a high carbohydrate meal, the blood glucose concentration can rise to concentrations much greater than 5 mM. What would be the effect of this concentration change on HK II activity in muscle tissue?

WHEN BLOOD GLUCOSE CONC IS INFINITLY HIGHER THAN Km THEN Vmax WILL BE ACHIEVED

c) Given the information and your answer in part b, what would be the net effect on the person’s blood glucose concentration after a high carbohydrate meal?

UNDER NORMAL CONDITION BLOOD GLUCOSE AT 5 mM conc is sufficient as energy to normal cells requirements so the excess glucose is stored in liver or muscle in glycogen form by insulin. If insulin system is defective then high glucose conc will lead to its toxicity.

gladiator answered 1 year ago

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