Podcast
Questions and Answers
What role does insulin play in glycogen synthesis in myocytes?
What role does insulin play in glycogen synthesis in myocytes?
Which of the following statements about carbohydrate regulation in liver cells is true?
Which of the following statements about carbohydrate regulation in liver cells is true?
What is the main difference between carbohydrate metabolism in muscles and liver cells?
What is the main difference between carbohydrate metabolism in muscles and liver cells?
What effect does epinephrine have on glycolysis in liver and muscle cells?
What effect does epinephrine have on glycolysis in liver and muscle cells?
Signup and view all the answers
Which of the following best describes the simultaneous action of hormones such as insulin?
Which of the following best describes the simultaneous action of hormones such as insulin?
Signup and view all the answers
What is the most common glycogen storage disease?
What is the most common glycogen storage disease?
Signup and view all the answers
What enzyme deficiency leads to Pompe Disease?
What enzyme deficiency leads to Pompe Disease?
Signup and view all the answers
Which process is primarily involved in elongating glycogen chains?
Which process is primarily involved in elongating glycogen chains?
Signup and view all the answers
Which condition is a result of deficiency in muscle glycogen phosphorylase?
Which condition is a result of deficiency in muscle glycogen phosphorylase?
Signup and view all the answers
What is a key characteristic of covalent modifications of enzymes?
What is a key characteristic of covalent modifications of enzymes?
Signup and view all the answers
Which component is responsible for priming glycogen synthesis?
Which component is responsible for priming glycogen synthesis?
Signup and view all the answers
What happens when the rate of conversion from substrate to product is equal to the reverse rate?
What happens when the rate of conversion from substrate to product is equal to the reverse rate?
Signup and view all the answers
The FDA approved a recombinant form of which enzyme in 2006 for treating Pompe Disease?
The FDA approved a recombinant form of which enzyme in 2006 for treating Pompe Disease?
Signup and view all the answers
What is the primary function of glycogen in the body?
What is the primary function of glycogen in the body?
Signup and view all the answers
Which type of bond links the glucose units in glycogen?
Which type of bond links the glucose units in glycogen?
Signup and view all the answers
Which of the following correctly describes the process of phosphorolysis in glycogen degradation?
Which of the following correctly describes the process of phosphorolysis in glycogen degradation?
Signup and view all the answers
Where is glucose-6-phosphatase predominantly found?
Where is glucose-6-phosphatase predominantly found?
Signup and view all the answers
What is the outcome of the debranching process in glycogen degradation?
What is the outcome of the debranching process in glycogen degradation?
Signup and view all the answers
Which of the following statements is true regarding muscle and adipose tissue cells?
Which of the following statements is true regarding muscle and adipose tissue cells?
Signup and view all the answers
Which enzyme is responsible for a continuous, small scale degradation of glycogen?
Which enzyme is responsible for a continuous, small scale degradation of glycogen?
Signup and view all the answers
Which process primarily consumes glucose-6-phosphate in the liver?
Which process primarily consumes glucose-6-phosphate in the liver?
Signup and view all the answers
What is the primary effect of insulin on glycogen synthesis?
What is the primary effect of insulin on glycogen synthesis?
Signup and view all the answers
Which hormone is responsible for increasing cyclic-AMP levels in the body?
Which hormone is responsible for increasing cyclic-AMP levels in the body?
Signup and view all the answers
Which of the following is directly inhibited by insulin during carbohydrate metabolism?
Which of the following is directly inhibited by insulin during carbohydrate metabolism?
Signup and view all the answers
In which tissue does glucagon primarily exert its effects?
In which tissue does glucagon primarily exert its effects?
Signup and view all the answers
What is the effect of glucagon on gluconeogenesis?
What is the effect of glucagon on gluconeogenesis?
Signup and view all the answers
Which of the following is NOT an effect of insulin?
Which of the following is NOT an effect of insulin?
Signup and view all the answers
What is the general role of phosphoprotein phosphatase related to insulin action?
What is the general role of phosphoprotein phosphatase related to insulin action?
Signup and view all the answers
Which pathway is primarily stimulated by epinephrine in muscle tissue?
Which pathway is primarily stimulated by epinephrine in muscle tissue?
Signup and view all the answers
What is the primary regulatory mechanism of PFK-1 in glycolysis?
What is the primary regulatory mechanism of PFK-1 in glycolysis?
Signup and view all the answers
Which hexokinase isozyme is primarily found in the liver?
Which hexokinase isozyme is primarily found in the liver?
Signup and view all the answers
What effect does fructose-2,6-bisphosphate have on glycolysis and gluconeogenesis?
What effect does fructose-2,6-bisphosphate have on glycolysis and gluconeogenesis?
Signup and view all the answers
How does the activity of glucokinase change when blood glucose levels increase?
How does the activity of glucokinase change when blood glucose levels increase?
Signup and view all the answers
What is the effect of ATP on pyruvate kinase activity in glycolysis?
What is the effect of ATP on pyruvate kinase activity in glycolysis?
Signup and view all the answers
Which enzyme initiates the gluconeogenesis pathway from pyruvate?
Which enzyme initiates the gluconeogenesis pathway from pyruvate?
Signup and view all the answers
What role does insulin play in the regulation of glycogen metabolism?
What role does insulin play in the regulation of glycogen metabolism?
Signup and view all the answers
Which of the following is an allosteric inhibitor of PFK-1?
Which of the following is an allosteric inhibitor of PFK-1?
Signup and view all the answers
What is the function of glycogen phosphorylase in the liver?
What is the function of glycogen phosphorylase in the liver?
Signup and view all the answers
Which enzyme is responsible for converting fructose-6-phosphate to fructose-1,6-bisphosphate?
Which enzyme is responsible for converting fructose-6-phosphate to fructose-1,6-bisphosphate?
Signup and view all the answers
What happens to glycogen phosphorylase when high levels of glucose are detected?
What happens to glycogen phosphorylase when high levels of glucose are detected?
Signup and view all the answers
What is the consequence of acetyl-CoA on the regulation of pyruvate?
What is the consequence of acetyl-CoA on the regulation of pyruvate?
Signup and view all the answers
Which molecule serves as a signal of high-energy status to inhibit glycolysis?
Which molecule serves as a signal of high-energy status to inhibit glycolysis?
Signup and view all the answers
Study Notes
Glucose and Glycogen Regulation
- Glucose levels in the blood (glycemia) are tightly controlled through various processes involving glucose production and consumption.
- Excess glucose is stored as glycogen, which cannot be stored in large quantities due to its osmotic nature.
- Glycogen is a branched polymer of glucose linked together through α(1→4) and α(1→6) linkages.
- Glycogen is primarily stored in the liver (up to 10% weight) and skeletal muscles (up to 1-2% weight).
Glycogen Degradation
- Glucose residues are removed from the non-reducing ends via phosphorolysis
- Glycogen phosphorylase catalyzes the removal of glucose-1-phosphate from glycogen.
- Debranching enzyme is involved in the removal of branches from the glycogen molecule.
- Glucose-1-phosphate is converted to glucose-6-phosphate.
- Glucose-6-phosphate can be used in glycolysis, the pentose pathway, or gluconeogenesis to regenerate glucose.
- Liver cells contain glucose-6-phosphatase, which is absent in muscle cells. This allows for the release of glucose into the bloodstream.
Glycogen Storage Diseases
- Glycogen storage diseases result from deficiencies in enzymes involved in glycogen metabolism.
- Pompe disease is a lysosomal (1→4)-glucosidase deficiency leading to glycogen accumulation in lysosomes.
- McArdle syndrome is caused by a deficiency in skeletal muscle glycogen phosphorylase.
- Von Gierke disease is the most common glycogen storage disease, resulting from a glucose-6-phosphatase deficiency.
Regulation of Glycolysis and Gluconeogenesis
- Glycolysis and gluconeogenesis are regulated to maintain a dynamic steady state. Regulation happens at the level of the three irreversible steps.
- Key enzymes in these pathways (e.g., PFK-1, pyruvate kinase, glucose-6-phosphatase) are regulated allosterically and/or via covalent modification.
- Fructose-2,6-bisphosphate plays a crucial regulatory role, activating glycolysis and inhibiting gluconeogenesis.
- ATP and citrate inhibit glycolysis.
- ADP and AMP activate glycolysis and inhibit gluconeogenesis.
- These pathways are regulated as a coordinated system to prevent futile cycles.
Regulation of Glycolysis at Hexokinase Level
- Hexokinase IV (glucokinase) in liver cells has a higher Km for glucose and is not inhibited by glucose 6-phosphate.
- This allows the liver to uptake and metabolize glucose even at low blood glucose concentrations.
Regulation of Glycolysis at PFK Level
- PFK-1 is allosterically regulated by ATP and citrate.
- Its activity is higher when ATP levels are low and citrate levels are high.
Regulation of Glycolysis at Pyruvate Kinase Level
- Pyruvate kinase is allosterically regulated by ATP, acetyl-CoA, fatty acids, and alanine.
- Insulin promotes the activation of pyruvate kinase in the liver.
Regulation of Glycogen Synthesis and Breakdown
- Glycogen synthase is activated by insulin and de-activated by glucagon.
- Glycogen phosphorylase is activated by glucagon, epinephrine, and AMP and inactivated by insulin and PP1.
Hormonal Regulation of Carbohydrate Metabolism
- Insulin stimulates glycogen synthesis and inhibits glycogen breakdown.
- Glucagon and epinephrine stimulate glycogen breakdown and inhibit glycogen synthesis.
- They have opposing effects on glycolysis and gluconeogenesis and on the different tissues.
Summary of Glycogen Regulation
- Coordinated regulation of glycolysis and gluconeogenesis is achieved to prevent futile cycles and maintain glucose homeostasis.
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
Related Documents
Description
Test your knowledge on the regulation of glucose and glycogen metabolism, including their storage, degradation, and biochemical pathways. This quiz covers key processes like glycolysis, gluconeogenesis, and the role of enzymes in glucose metabolism.