Glucose is transported across the membrane by several isoforms of the GLUT trans

Question

Glucose is transported across the membrane by several isoforms of the GLUT transporter. GLUT1,3,4 have KM 0.3mM while GLUT2 has a KM-5mM. If the effective concentration of the enzyme is 18.800000 M, [Glucose,lood-3200000 mM and [Glucoselnracelular -21.200000 M, what is the flux, J of glucose into the cell? Consider that kcat-10/sec for all enzymes. J M/sec = GLUT1,3,4 GLUT2 Part 2 (1 point) For GLUT4 receptors, the activity of insulin increases the GLUT4 concentration to increase to 0.920000 mM on the cell surface. What is the flux of glucose into the cell under the stimulation of insulin? M/sec

Explanation / Answer

1) By the following equation : Vmax= k [ E] ; For GLUT 1,3 4 : Vmax= 0.3 mM x 18.8uM = 5640 uM

For forward reaction we use the blood glucose concentration to calculate flux

Forward reaction velocity , Vf =Vmax  [S] / [S] + Km = 5640uM x (3200 uM/ 3200uM + 300 ) = 5156.57 uM/s

For reverse reaction we use the intracellular glucose concentration

Reverse reaction velocity Vr = Vmax  [S] / [S] + Km = 5640 uM x ( 21.2 uM / 21.2 + 300 uM )= 6.204 uM/sec

Flux, J = Vf - Vr = 5156.57 - 6.204 = 0. 00478 M/ sec = J glut1,3,4

Similarly, J glut2 = 0.234 M/sec

Part 2 :

By using the same equations above : V = Vmax x [ S] / [S] + Km and J = Vf - Vr

We get, glucose flux for GLUT4 is 0.234 M/sec

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