Chapter 10, Problem 15P

The concentration of glucose in your circulatory system is maintained near 5.0 mM by the actions of the pancreatic hormones glucagon and insulin. Glucose is imported into cells by protein transporters that are highly specific for binding glucose. Inside the liver cells the imported glucose is rapidly phosphorylated to give glucose-6-phosphate (G-6-P). This is an ATP-dependent process that
consumes 1 mol ATP per mol of glucose.

a. The process of phosphorylating the glucose after it has been transported into the cell is considered a form of active transport —called "transport by modification” though ATP is not bound by the transporter protein, nor is ATP hydrolysis directly involved in the movement of glucose across the membrane. Explain the thermodynamic basis for this form of active transport (Hint: Consider Le Chatelier's principle.)
b. Given
ATP = 4.7 mM; ADP = 0.15 mM; P_i = 6.1 mM, calculate the theoretical maximum concentration of G-6-P
inside a liver cell at 37 ^oC, pH = 7.2 when the glucose concentration outside the cell (i.e., [glucose]_outside) is 5.0 mM:

ATP + glucose_inside→ADP + glucose-6-phosphate + H+
For
ATP + H₂O →ADP + P_i + H+ ΔG^o’ = -32.2 kJ/mol and for
G-6-P + H₂O →Glucose + P_i ΔG^o’ = -13.8 kJ / mol