Glucose Metabolism and Regulation Quiz

Metabolism and Regulation of Glucose

• Pentose phosphate shunt produces NADPH and pentose phosphates
• Glucose-6-Phosphate dehydrogenase is allosterically and hormonally regulated
• Glycogenesis and glycogenolysis pathways involve key enzymes
• Regulation of glycogen synthase and glycogen phosphorylase is allosteric and hormonal
• Glycolysis involves PFK1, hexokinase/glucokinase, and pyruvate kinase as regulated enzymes
• Hexokinase catalyzes glucose to G6P and is inhibited by glucose-6-phosphate
• PFK1 is under complex allosteric regulation, inhibited by ATP and citrate
• PFK1 is activated by fructose 2,6-bisphosphate, which stimulates glycolysis and inhibits gluconeogenesis
• Pyruvate kinase is allosterically regulated by ATP, acetyl-CoA, and fatty acids
• Insulin promotes the transcription of glycolytic enzymes, while glucagon reduces their expression
• Fructose metabolism occurs predominantly in the liver and is faster than glucose metabolism
• The first two bypass reactions are the main regulated reactions of gluconeogenesis

Glycogenesis and Glycogenolysis: Key Concepts

• Glycogenesis involves the transfer of 4-8 glucose residues to a branch point by the branching enzyme, also known as amyloα(1,41,6) glucosyl transferase.
• Glycogen synthase requires a primer containing pre-formed (alpha14) polyglucose chain with at least 4-8 glucose residues, found within glycogenin.
• Glycogenolysis is the breakdown of glycogen into glucose units, occurring in the liver and muscle.
• Glucose is removed from nonreducing ends of glycogen by the enzyme glycogen phosphorylase, releasing glucose-1-P.
• A de-branching enzyme transfers glucose residues from the branch to another non-reducing end and removes the final glucose residue in the alpha(16) linkage.
• Glucose-1-P is converted to glucose-6-P by phosphoglucomutase, which can be converted to glucose in the liver but not in muscles.
• Glycogen synthase is allosterically activated by glucose-6-P, while glycogen phosphorylase is allosterically inhibited by glucose-6-P and ATP.
• Hormonally, glucagon and epinephrine activate glycogen phosphorylase and inhibit glycogen synthase through PKA phosphorylation, while insulin promotes glycogenesis by inactivating PKA and activating protein phosphatase 1.
• Hormonal regulation involves covalent modification of glycogen metabolism, with glucagon and epinephrine activating glycogen phosphorylase and insulin promoting glycogenesis.
• Insulin activates protein phosphatase 1, which removes the phosphate group from glycogen synthase and glycogen phosphorylase kinase, inhibiting glycogenolysis.
• The covalent modification of glycogen metabolism is under hormonal control, with glucagon and epinephrine activating glycogen phosphorylase and inhibiting glycogen synthase, while insulin has the opposite effect.
• The text provides references to Alberts et al. Molecular Biology of the Cell and Lehninger Principles of Biochemistry, as well as study questions related to glycolysis, gluconeogenesis, the pentose phosphate shunt, glycogenesis, and glycogenolysis.

Glycogenesis and Glycogenolysis: Key Concepts

• Glycogenesis involves the transfer of 4-8 glucose residues to a branch point by the branching enzyme, also known as amyloα(1,41,6) glucosyl transferase.
• Glycogen synthase requires a primer containing pre-formed (alpha14) polyglucose chain with at least 4-8 glucose residues, found within glycogenin.
• Glycogenolysis is the breakdown of glycogen into glucose units, occurring in the liver and muscle.
• Glucose is removed from nonreducing ends of glycogen by the enzyme glycogen phosphorylase, releasing glucose-1-P.
• A de-branching enzyme transfers glucose residues from the branch to another non-reducing end and removes the final glucose residue in the alpha(16) linkage.
• Glucose-1-P is converted to glucose-6-P by phosphoglucomutase, which can be converted to glucose in the liver but not in muscles.
• Glycogen synthase is allosterically activated by glucose-6-P, while glycogen phosphorylase is allosterically inhibited by glucose-6-P and ATP.
• Hormonally, glucagon and epinephrine activate glycogen phosphorylase and inhibit glycogen synthase through PKA phosphorylation, while insulin promotes glycogenesis by inactivating PKA and activating protein phosphatase 1.
• Hormonal regulation involves covalent modification of glycogen metabolism, with glucagon and epinephrine activating glycogen phosphorylase and insulin promoting glycogenesis.
• Insulin activates protein phosphatase 1, which removes the phosphate group from glycogen synthase and glycogen phosphorylase kinase, inhibiting glycogenolysis.
• The covalent modification of glycogen metabolism is under hormonal control, with glucagon and epinephrine activating glycogen phosphorylase and inhibiting glycogen synthase, while insulin has the opposite effect.
• The text provides references to Alberts et al. Molecular Biology of the Cell and Lehninger Principles of Biochemistry, as well as study questions related to glycolysis, gluconeogenesis, the pentose phosphate shunt, glycogenesis, and glycogenolysis.