When the blood glucose concentration is low, the pancreas secretes glucagon to signal the liver to produce glucose and glucose-1-phosphate. Which metabolic steps are involved in this biosignaling pathway?
I. Inactivation of glycogen synthase via phosphorylation by protein kinase A
II. Activation of glycogen synthase via phosphorylation by protein kinase A
III. Activation of phosphofructokinase-2 via phosphorylation by protein kinase A
IV. Activation of fructose-2,6-bisphosphatase via phosphorylation by protein kinase A
V. Activation of phosphofructokinase-1 by fructose-2,6-bisphosphate
VI. Inhibition of fructose-1,6-bisphosphatase by fructose-2,6-bisphosphate
VII. Inactivation of pyruvate kinase via phosphorylation by protein kinase A
A. I, IV, and VII.
B. II
C. I and IV.
D. I, III, V, VI, and VII.
Which biochemical steps are involved in the glucagon-triggered activation of gluconeogenesis?
I. Activation of fructose-2,6-bisphosphatase via phosphorylation by protein kinase A
II. Inactivation of fructose-2,6-bisphosphatase via phosphorylation by protein kinase A
III. Activation of phospholipase C
IV. Inactivation of phospholipase C
V. Release of calcium
VI. Sequestration of calcium
VII. Phosphorylation of FoxO1
VIII. Dephosphorylation of FoxO1
IX. Increased expression of PEP carboxykinase
X. Phosphorylation of PEP carboxykinase
XI. Formation of additional PEP, which is a glycolytic intermediate
XII. Degradation of PEP, which is a glycolytic intermediate
A. I, III, V, VII, X, and XI.
B. II, III, V, VII, IX, and XI.
C. I, III, VI, VII, IX, and XII.
D. I, III, V, VII, IX, and XI.
When the blood glucose concentration is high, the level of cAMP in the liver decreases and glycolytic flux increases. Which biochemical steps occur under this condition?
I. Protein kinase A is activated.
II. Protein kinase A is not activated.
III. Phosphofructokinase-2 is activated via phosphorylation by protein kinase A.
IV. Phosphofructokinase-2 is activated due to the lack of phosphorylation by protein kinase A.
V. Fructose-2,6-bisphosphatase is activated via phosphorylation by protein kinase A.
VI. Fructose-2,6-bisphosphatase is activated due to the lack of phosphorylation by protein kinase A.
VII. Phosphofructokinase-1 is activated by fructose-2,6-bisphosphate.
VIII. Phosphofructokinase-1 is inhibited by fructose-2,6-bisphosphate.
IX. Fructose-1,6-bisphosphatase is activated by fructose-2,6-bisphosphate.
X. Fructose-1,6-bisphosphatase is inhibited by fructose-2,6-bisphosphate.
A. II, IV, VIII, and IX.
B. II, IV, VII, and X.
C. I, III, VII, and X.
D. II and V.
After glucagon stimulates glucose production via glycogenolysis and/or gluconeogenesis in a liver cell, which steps are required to transport glucose to other cells in the body?
A. Glucose is transported to other cells by the carrier protein GLUT-1.
B. Glucose-6-phosphate is converted to glucose by GLUT-1.
C. Glucose cannot leave the liver cell.
D. Glucose exits the liver cell via GLUT-1 and enters the bloodstream.
In certain smooth muscles, glucagon increases the amount of glucose available for glycolysis; under this condition, which enzyme is required to convert glucose-1-phosphate into a glycolytic intermediate?
A. No enzyme is needed for this conversion.
B. G6Pase.
C. Glucokinase (or hexokinase).
D. Phosphoglucomutase.