Lecture 39 Flashcards
In the liver, what molecules use negative feedback to prevent the conversion of glycogen to glucose 1-phosphate?
1) Glucose 6-phosphate
2) ATP
3) Glucose
In the liver, what molecule uses positive feedback to convert glucose 1-phosphate to glycogen?
Glucose 6-phosphate
In muscle, what molecules use negative feedback to prevent the conversion of glycogen to glucose 1-phosphate?
1) Glucose 6-phosphate
2) ATP
In muscle, what molecules use positive feedback to convert glycogen to glucose 1-phosphate?
1) Ca2+
2) AMP
In muscle, what molecule uses positive feedback to convert glucose 1-phosphate to glycogen?
Glucose 6-phosphate
What is glycogen storage disease type 1 (Von Gierke disease)?
1) Enzyme defect: Glucose-6-phosphatase
2) Glycogen structure: Normal
3) Organs involved: Liver, Kidney
4) Characteristics: Hypoglycemia, enlarged liver, lactic acidosis, ketosis, growth retardation, delayed puberty, progressive renal disease, hyperuricemia
5) Increased levels of glucose 6-phosphate activate glycogen synthase b, the normally inactive form
6) Treatment: Nocturnal gastric infusions of glucose or regular administration of uncooked cornstarch
What does glucose-6-phosphatase do?
Glucose 6-phosphatase is an enzyme that hydrolyzes glucose-6-phosphate, resulting in the creation of a phosphate group and free glucose
What is ketosis?
1) Ketone bodies are formed by ketogenesis when liver glycogen stores are depleted
2) Ketosis is a metabolic state where most of the body’s energy supply comes from ketone bodies in the blood, in contrast to a state of glycolysis where blood glucose provides most of the energy
What is glycogen storage disease type 2 (Pompe disease)?
1) Enzyme defect: alpha glucosidase (lysosomal)
2) Glycogen structure: Normal
3) Organs involved: Generalized
4) Characteristics: Enlarged heart, cardiorespiratory failure
What is glycogen storage disease type 3 (Cori disease)?
1) Enzyme Defect: Glycogen debranching enzyme
2) Glycogen structure: Short outer chains on fasting
3) Organs involved: Generalized
4) Characteristics: Englarged liver, moderate hypoglycemia, acidosis
What is glycogen storage disease type 4 (Andersen disease)?
1) Enzyme defect: Glycogen branching enzyme
2) Glycogen structure: Few branch points
3) Organs involved: Generalized
4) Characteristics: Cirrhosis, progressive liver failure
What is glycogen storage disease type 5 (McArdle disease)?
1) Enzyme defect: Muscle glycogen phosphorylase
2) Glycogen structure: Normal
3) Organs involved: Skeletal muscle
4) Characteristics: Muscle cramps on exercise
5) Similar symptoms are seen in glycogen storage disease type 7 in which there is decreased activity of phosphofructokinase activity in muscle
What is glycogen storage disease type 6 (Hers disease)?
1) Enzyme defect: Liver glycogen phosphorylase
2) Glycogen structure: Normal
3) Organs involved: Liver
4) Characteristics: Enlarged liver, moderate hypoglycemia and mild acidosis
5) A deficiency of liver glycogen phosphorylase kinase has been classified as either Type 8 or included in type 6. This condition is X-linked unlike the other glycogen storage diseases that have an autosomal recessive inheritance
Which two enzymes that either produce or break down glycogen are reciprocals of each other?
Glycogen synthase & glycogen phosphorylase
Describe the cAMP dependent glycogen synthase inactivation pathway (formation of glycogen)
1) Glucagon (liver) + Epinephrine (primarily muscle; also liver) receptors, when activated, cause Adenylyl Cyclase to convert ATP –> cAMP
2) cAMP activates cAMP-dependent protein kinase A by binding to its 2 regulatory subunits (R)
3) The catalytic subunits (C) can then phosphorylate Glycogen synthase a (active form) to produce Glycogen synthase b (inactive form)
4) Insulin can cause Glycogen synthase b to be dephosphorylated by protein phosphatase 1, reforming the active form of glycogen synthase a
