.Suppose a patient is brought into your clinic in a hypoglycemic state with a bl

Question

.Suppose a patient is brought into your clinic in a hypoglycemic state with a blood glucose of 3.5mM. The patient is disoriented and slurring his speech and feeling woozy. The Kt for GLUT1, expressed in brain cells, is 1.5mM. The Km for the hexokinase I, expressed in brain cells, is 0.1mM. What is the velocity of transport into these cells as a percentage of Vmax? What is the velocity of glucose 6-phosphate production in these cells as a percentage of Vmax? Which of these protein activities explains the symptoms in the patient?

Explanation / Answer

a) What is the velocity of transport into these cells as a percentage of Vmax?

Ans.

given - Km for GLUT1 expressed in brain cells= 1.5mM, blood glucose= 3.5mM

V0 = Vmax [S] / Km+ S = Vmax 3.5/ 1.5+3.5 = 3.5/5 Vmax = 0.7 Vmax, V0 = 0.7 Vmax

SO, V0 = 70 percent Vmax .

b) What is the velocity of glucose 6-phosphate production in these cells as a percentage of Vmax?

Ans. glucose 6-phosphate is produced by hexokinse I in brain.

given, Km for hexokinse I expressed in brain cells= 0.1 mM, blood glucose= 3.5mM

V0 = Vmax [S] / Km+ S = Vmax 3.5/ 0.1+3.5 = 3.5/3.6 Vmax = 0.97222 Vmax, V0 = 0.97222 Vmax

SO, V0 = 97.22 percent Vmax .

c) Which of these protein activities explains the symptoms in the patient?

Ans. GLUT1, as these symptoms are characterstic of low glucose availability to brain and GLUT1 is involved in the transportation of glucose in brain.

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