Glycogen Flashcards
What are the ways to generate ATP in skeletal muscle during exercise?
- Aerobic Cellular Respiration
- Anaerobic Glycolysis
- Direst phosphorylation of ADP by creatine kinase
What 3 amino acids are needed for the synthesis of creatine?
Glycine, arginine, and methionine
___ acts as high energy reservoir in the muscle
Creatine phosphate
___ can be rapidly mobilized to form ATP during the first few moments of intense muscular contraction
Creatine phosphate
The presence of this isoenzyme is indicative of heart damage and is used in the diagnosis of myocardial infarction.
Creatine kinase known as CK-MB in the plasma
Creatine and creatine phosphate form ___ when degraded
Creatinine
Creatinine is a normal constituent of ___
Urine
The amount of creatinine excreted in the urine is ___ to the total creatine phosphate in the body, therefore to the muscle mass
Proportional
If the muscle mass decreases, such as in paralysis or muscle dystrophy, the creatinine content in the urine ___
Decreases
Determination of creatinine level in plasma is an important investigation in ___
Kidney disease
___ of plasma creatinine is a notable feature seen in renal failure
Increase
Where are the main stores of glycogen found?
Liver and Muscle
How many grams of glycogen does well-fed adult liver contain?
~ 100g (10% of fresh weight)
How many grams of glycogen does resting muscle contain?
~ 400g (1-2% of fresh weight)
When is muscle glycogen extensively degraded?
During strenuous exercise
When is liver glycogen degraded?
For the maintenance of blood glucose level
The synthesis of glycogen is called
Glycogenesis
The catabolism of glycogen is called
Glycogenolysis
What are the major enzymes in glycogenesis?
Glycogen synthase and branching enzyme
Where is the subcelluar site of glycogenesis?
Cytosol
What energy forms are required for glycogenesis?
ATP and UTP
What transforms Glucose-6-phophate to Glucose-1-phosphate?
Phosphoglucomutase
What transforms Glucose-1-phosphate to UDP Glucose (UDPG)?
UDPG pyrophosphorylase
What transforms UDP Glucose to Glycogen (with 1->4 glucosyl units)?
Glycogen synthase
What transforms Glucose with 1->4 branching to Glucose with 1->4 and 1->6 glucosyl units?
Branching Enzyme
What serves as a primer in Glycogenesis?
Glycogenin
What acts as a carrier of the glucose for the synthesis of glucose?
UDPG
What incorporates glucose units to the glycogen primes by forming alpha 1->4 glycosidic bonds?
Glycogen sythase
Where does branching enzyme from glucose residues to attach it to another glucosyl residue? How many are removed?
Removed from the nonreducing end; a set of 6-8
What are the major enzymes of glycogenolysis?
Glycogen phosphorylase and debranching enzyme (with 4:4 transferase and 1:6 glucosidase activity)
What is the sub cellular site of glycogenolysis?
Cytosol
What are the end products of glycogenolysis?
Liver: glucose
Muscle: glucose-6-phophate
What is the major product formed as a result of glycogenolysis?
Glucose-1-phosphate
Glycogen phosphorylase is ___ dependent
PLP dependent
What is the coenzyme form of B-complex vitamin, Pyridoxine (B6)?
PLP (Pyridoxal phosphate)
This enzyme sequentially removes the glycosyl residues from the non-reducing ends as glucose-1-phosphate by phosphorolysis?
Glycogen phosphorylase
A small amount of glycogen is continuously degraded by the lysosomal enzyme ___
alpha-glucosidase (acid maltase/ alpha 1,4-glucosidase)
Deficiency of this enzyme causes accumulation of glycogen in lysosomes (Pompe disease or type II glycogen storage disease)
Alpha-glucosidase
In skeletal muscle, ___ occurs during active exercise, ___ begins as soon as the muscle is at rest
Glycogenolysis; glycogenesis
In the liver, ___ accelerates in the well-fed state, ___ increases in the fasting state
Glycogenesis; glycogenolysis
What are the main regulatory enzymes for glycogen metabolism?
Glycogen synthase and glycogen phosphorylase
At what two levels is glycogen metabolism regulated?
Hormonal (by phosphorylation/dephosphorylation): to meet the needs of the whole body
Allosteric (by effector molecules): regulation to meet the needs of a particular tissue
___ regulates glycogen metabolism in the liver, but not in the muscles?
Glucagon
___ exert their action on both the liver and the muscles
Insulin and Epinephrine
What is type 1a glycogen storage disease? What is it’s deficiency?
Von Gierke Disease
Deficiency of glucose-6-phosphatase in liver
What is type 1b glycogen storage disease? What is it’s deficiency?
No name
Deficiency of glucose-6-phosphate translocate in ER
What is type II glycogen storage disease? What is it’s deficiency?
Pompe disease
Deficiency of lysosomal alpha-glucosidase (acid maltase)
What is type III glycogen storage disease? What is it’s deficiency?
Cori disease
Deficiency of liver and muscle deb ranching enzyme
What is type IV glycogen storage disease? What is it’s deficiency?
Andersen disease/ amylopectinosis
Deficiency of branching enzyme
What is type V glycogen storage disease? What is it’s deficiency?
McArdle disease
Deficiency of muscle glycogen phosphorylase (myophosphorylase); liver enzyme is normal
What is type VI glycogen storage disease? What is it’s deficiency?
Hers’ disease
Deficiency of glycogen phosphorylase in the liver
