49 Questions
Which pathway involves the conversion of glucose-6-phosphate to 6-phosphogluconolactone?
Pentose phosphate shunt
Which process involves the irreversible step catalyzed by phosphofructokinase-1?
Glycolysis
Which process involves the conversion of pyruvate to phosphoenolpyruvate?
Gluconeogenesis
Which pathway involves the synthesis of glycogen from glucose?
Glycogenesis
Which enzyme is responsible for catalyzing glucose to G6P and is inhibited by glucose-6-phosphate?
Hexokinase
What stimulates glycolysis and inhibits gluconeogenesis by activating PFK1?
Fructose 2,6-bisphosphate
Which hormone promotes the transcription of glycolytic enzymes?
Insulin
Which pathway involves key enzymes in glycogenesis and glycogenolysis?
Glycogen metabolism
What is the main regulated reaction of gluconeogenesis?
Conversion of fructose-1,6-bisphosphate to fructose-6-phosphate
Which molecule allosterically regulates pyruvate kinase?
ATP
What is the primary product of the pentose phosphate shunt?
NADPH
What inhibits PFK1 in glycolysis?
Fructose 2,6-bisphosphate
Which hormone reduces the expression of glycolytic enzymes?
Glucagon
Which pathway involves the conversion of pyruvate to oxaloacetate?
Gluconeogenesis
Which molecule activates PFK1 in glycolysis?
Fructose 1,6-bisphosphate
Which pathway predominantly occurs in the liver and is faster than glucose metabolism?
Fructose metabolism
What is the primary function of the branching enzyme in glycogenesis?
Transfer of 4-8 glucose residues to a branch point
Which enzyme is responsible for removing glucose from nonreducing ends of glycogen?
Glycogen phosphorylase
What is the fate of glucose-1-P in glycogenolysis?
Converted to glucose-6-P
What is the role of insulin in glycogen metabolism?
Promotes glycogenesis by inactivating PKA and activating protein phosphatase 1
Which molecule allosterically activates glycogen synthase?
Glucose-6-P
Which hormone promotes glycogenolysis and inhibits glycogen synthase through PKA phosphorylation?
Glucagon
What is the function of the de-branching enzyme in glycogenolysis?
Transfers glucose residues from the branch to another non-reducing end and removes the final glucose residue in the alpha(16) linkage
What is the main hormonal regulator of glycogen metabolism?
Glucagon
Which enzyme is activated by glucagon and epinephrine in glycogenolysis?
Glycogen phosphorylase
What is the effect of insulin on glycogenolysis?
Inhibits glycogenolysis
What is the role of glucagon and epinephrine in glycogen metabolism?
Activate glycogen phosphorylase and inhibit glycogen synthase
Which enzyme is allosterically inhibited by glucose-6-P and ATP?
Glycogen synthase
Which enzyme catalyzes the conversion of pyruvate to oxaloacetate?
Pyruvate carboxylase
What reaction does FBP-1 catalyze?
Conversion of fructose-1,6-bisphosphate to fructose-6-phosphate
Which enzyme is needed to commit glucose-6-phosphate to glycolysis?
Phosphofructokinase-1
Why is the pentose phosphate pathway called a 'shunt'?
It diverts glucose-6-phosphate from glycolysis to produce NADPH and pentose phosphates
What is the primary fate of ribose-5-phosphate in the pentose phosphate pathway?
Used for nucleotide synthesis
In glycogen metabolism, which enzyme catalyzes the addition of UDP-glucose to the nonreducing end of glycogen?
Glycogen synthase
What type of link is formed when glucose is added to the nonreducing end of glycogen during glycogenesis?
α-1,4-glycosidic bond
What is the primary function of the branching enzyme in glycogenesis?
Catalyzes the formation of α-1,6-glycosidic bonds in glycogen
Which enzyme is responsible for converting glucose-6-phosphate to 6-phosphogluconolactone in the pentose phosphate pathway?
Glucose-6-phosphate dehydrogenase
What inhibits glucose-6-phosphate dehydrogenase in the pentose phosphate pathway?
High NADPH:NADP+ ratio
What is the role of the branching enzyme in glycogenesis?
It transfers glucose residues from the branch to another non-reducing end and removes the final glucose residue in the alpha(1$\to$6) linkage.
What is the fate of glucose-1-P in glycogenolysis?
It is converted to glucose-6-P by phosphoglucomutase.
Which molecule allosterically activates glycogen synthase?
Glucose-6-P
What is the primary function of insulin in glycogen metabolism?
To promote glycogenesis by inactivating PKA and activating protein phosphatase 1.
What is the effect of glucagon and epinephrine on glycogen metabolism?
They activate glycogen phosphorylase and inhibit glycogen synthase through PKA phosphorylation.
What is the primary function of the de-branching enzyme in glycogenolysis?
It transfers glucose residues from the branch to another non-reducing end and removes the final glucose residue in the alpha(1$\to$6) linkage.
What is the main hormonal regulator of glycogen metabolism?
Glucagon
What is the fate of ribose-5-phosphate in the pentose phosphate pathway?
It is used for nucleotide synthesis.
Which enzyme is responsible for removing glucose from nonreducing ends of glycogen?
Glycogen phosphorylase
What inhibits glucose-6-phosphate dehydrogenase in the pentose phosphate pathway?
Glucose-6-P
What is the role of glucagon and epinephrine in glycogen metabolism?
They activate glycogen phosphorylase and inhibit glycogen synthase through PKA phosphorylation.
Study Notes
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(1,41,6) glucosyl transferase.
- Glycogen synthase requires a primer containing pre-formed (alpha14) 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(16) 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(1,41,6) glucosyl transferase.
- Glycogen synthase requires a primer containing pre-formed (alpha14) 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(16) 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.
Test your knowledge of metabolism and regulation of glucose with this quiz covering key enzymes, pathways, hormonal and allosteric regulation, and the concepts of glycogenesis and glycogenolysis. Dive into the intricacies of glucose metabolism and hormonal control, and challenge yourself with study questions related to glycolysis, gluconeogenesis, and the pentose phosphate shunt.
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