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60 Cards in this Set
- Front
- Back
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How much glycogen is typically present in the liver?
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10% of its weight is glycogen
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how much glycogen is typically present in the muscle?
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1-2% of its weight is glycogen
has 2X the amount of glycogen than liver because it's a bigger tissue than the liver |
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Can the levels of glycogen stores in the liver and muscle be significantly changed?
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YES
A carbohydrate restricted diet would decrease the glycogen levels in both the liver and the skeletal muscle A diet high in carbohydrates would increase glycogen levels in both the liver and the muscle With intense training and a diet that is high in carbohydrates, athletes can get their muscle glycogen levels up close to 800 grams |
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What kind of skeletal muscle forms glycogen?
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Every cell form
Type I, IIA, IIB |
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what kind of skeletal muscle has the highest concentration of glycogen?
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Type IIB
fast twitch glycolytic |
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What kind of skeletal muscle has the highest concentration of triglycerides?
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Type I
Slow twitch |
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Why do we need a glycogen primer for synthesizing glycogen?
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glycogen synthesis cannot begin in response to insulin without a primer
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what is the primer for glycogen synthesis?
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Glycogenin
a protein that is an enzyme |
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what is Glycogenin used for?
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primer for glycogen synthesis
is used to form 8 glucose residues that are needed to prime glycogen synthase |
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what makes Glycogenin?
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primer for glycogen synthesis
need activated glucose to from the primer and glycogen Uridine diphosphate glucose (UDP-glucose) is the immediate precursor for glycogen synthesis |
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List the 5 enzymes that are required for glycogen synthesis
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1. Glucokinase
2. Phosphoglucomutase 3. UDP-glucose pyrophosphorylase 4. Glycogen synthase 5. Glucan Transferase |
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what enzyme is the rate limiting enzyme for glycogen synthesis?
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Glycogen synthase
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what is the branching enzyme for glycogen synthesis?
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Glucan Transferase
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why is glycogen highly branched?
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-to have multiple sites of phosphorylation and synthase
-synthesis and hydrolysis occur at the reducing ends -to provide a very large number of reducing ends where synthesis of new glycogen can occur and where hydrolysis can also occur -allows for much faster synthesis and much faster breakdown -each reducing end has both glycogen synthase and glycogen phosphorylase attached to it |
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what forms the branching points on glycogen?
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Glycogen synthase forms alpha-1,6-bond branch point
Glucan transferase forms alpha-1,6-bond branch point this is the branching enzyme branching enzyme cleaves a 7 piece unit off the straight chain formed by glycogen synthase and transfers it to the number 6 hydroxyl group of glucose that is at least 4 residues away from the last branch point and forms an alpha 1,6 glycosidic bond |
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Explain the difference between glycogen synthase A and glycogen synthase B
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Glycogen Synthase A: aka I form
-activity is INDEPENDENT of glucose-6-phosphate levels -this form is not phosphorylated Glycogen synthase B: aka D form -activity requires the PRESENCE of glucose-6-phosphate -form has been phosphorylated under hormonal control -even though phosphorylation is intended to inactivate glycogen synthase, glucose-6-phosphate can make it active. |
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What can activate glycogen synthase if it is phosphorylated?
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Glucose-6-phosphate
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what is the function of glycogen synthase?
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Enzyme involved in converting Glucose to Glycogen
It takes short polymers of glucose and converts them into long polymers |
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what regulates Glycogen Synthase?
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Glucose-6-Phosphate
Phosphorylation Insulin Glycogen synthase kinase AMPK Protein Kinase A |
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why would carbohydrate loading help surgery patients?
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carbohydrate loading is used in healthcare to optimize the conditions of the patients prior to surgery.
maximizes the glycogen stores in the muscles |
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what is the preferred storage and metabolic fuels for the brain?
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Storage: None mostly, little glycogen in the cerebral cortex
Fuel: Glucose (very little ketone bodies) |
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what is the preferred storage and metabolic fuels for the liver?
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Storage: Glycogen and Triglycerides
Fuel: Amino Acids |
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what is the preferred storage and metabolic fuels for adipose?
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storage: Triglycerides
Fuel: Fatty acids |
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what is the preferred storage and metabolic fuels for the Cardiac muscle?
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Storage: Glycogen
Fuel: Resting state: Triglycerides Exercise: Lactic acid |
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what is the preferred storage and metabolic fuels for the skeletal muscle?
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Storage: Glycogen (only in resting, active uses up glycogen)
Fuel: Resting: Fatty acids Exercise: Glucose |
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what are the 5 major hormones that regulate carbohydrate metabolism?
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Insulin
Glucagon Epinephrine Cortisol Growth Hormone |
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How does Insulin regulate carbohydrate metabolism?
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Long term control
Decreases Glucose (Cell surface receptor) Stops: Gluconeogenesis, Glucogenolysis Increases: Glycolysis, Glycogen synthesis |
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how does Glucagon regulate carbohydrate metabolism?
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Long term control compared to Epinephrine
Increases Glucose (Cell surface receptor) Stops: Glycogen Synthesis & Glycolysis Increases: Glycogenolysis and Gluconeogenesis |
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How does Epinephrine regulate carbohydrate metabolism?
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Compare to glucagon this is short term
Fight or Flight reaction Increases Glucose (cell surface receptor) Stops: Glycolysis, Glycogen breakdown Increases: Glycogen synthesis, Gluconeogenesis, protein breakdown, amino acid metabolism |
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how does Growth Hormone regulate carbohydrate metabolism?
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Increases Glucose (triggers liver to release IGF-1 & 2)
Stops: Decreases glucose up-take by muscle Increases: Gluconeogenesis in liver, lipolysis in adipose, protein synthesis in muscle |
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List the 5 enzymes that are required for glycogen hydrolysis
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Phosphorylase
Transferase Phosphoglucomutase Glucose-6-Phophatase Debranching Enzyme |
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what does phosphorylase do in glycogen hydrolysis?
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Rate limiting enzyme
Removes end of Glucose Adds Pi Forms Glucose-1-Phosphate |
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what does transferase do in glycogen hydrolysis?
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moves 3 glucose units
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what does debranching enzyme do in glycogen hydrolysis?
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two activities
alpha-1,6-glucosidase and transferase Cuts Alpha-1,6-unit |
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what does phosphoglucomutase do in glycogen hydrolysis?
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Converts Glucose-1-PHosphate to Glucose-6-Phosphate
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what does Glucose-6-Phosphatase do in glycogen hydrolysis?
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Liver, Kidney, Gut
Doesn't require transporter to move glucose out of liver and kidney Removes phosphate: Glucose-6-PHosphate > Glucose + Pi |
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List the 6 inhibitors of glycogen phosphorylase
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Glucose
Caffeine Creatine Phosphate ATP Glucose-6-Phosphate Phosphoprotein Phosphatase-1 |
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how does Glucose INHIBIT glycogen phosphorylase?
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Binds phosphorylase A to inhibit (TENSE state)
Promotes dephosphorylation of A by stimulating Phosphoprotein Phosphatase-1 LIver only: binds phosphorylase B and decreases activity |
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how does Caffeine INHIBIT glycogen phosphorylase?
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Binds phosphorylase A & B and inhibits by converting to tense state
Increases cAMP levels > increases PKA PKA changes B form to A form by triggering phosphorylation of B form via phosphorylase kinase |
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how does Creatine Phosphate INHIBIT glycogen phosphorylase?
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Skeletal Muscle ONLY
binds to phosphorylase A and converts to tense state |
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how does ATP INHIBIT glycogen phosphorylase?
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binds phosphorylase B and froms tense state
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how does Phosphoprotein Phosphatase-1 INHIBIT glycogen phosphorylase?
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removes phosphate from phosphorylase A converting it to less active B form
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what does a PP-1 inhibitor do?
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decreases activity of PP-1
PKA inhibits PP-1 from Epi & Glucagon Liver only: insulin and Glucose increase PP-1 activity |
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If the liver increases the activity of PP-1 via insulin and glucose what does this cause?
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decreases glycogen breakdown
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List the 4 activators of glycogen phosphorylase
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AMP
Glycogen Calcium Protein Kinase A |
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How does AMP activate Glycogen Phosphorylase?
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binds to phosphorylase B and increases its activity forming the relaxed state
more pronounced in muscle due to higher AMP levels generated by active muscle |
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How does Glycogen activate Glycogen Phosphorylase?
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binds to phosphorylase B and increases the activity of B by putting into the relaxed state
helps prevent the build up of too much glycogen in a cell |
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How does Calcium activate Glycogen Phosphorylase?
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Binds to calmodulin in phosphorylase kinase B to make it active
This enzyme converts Glycogen Phosphorylase B to A via epinephrine binding alpha-adrenergic receptors |
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How does Protein Kinase A activate Glycogen Phosphorylase?
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Phosphorylates Phosphorylase Kinase B to activate it converting B to A
PKA can be formed in response to glucagon or epinephrine |
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Explain how we get maximum glycogen breakdown in skeletal muscle when we exercise
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Exercise produces maximum activity for Phosphorylase Kinase
This gives the maximum glycogen breakdown in both liver and skeletal muscle |
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Describe the specific cascades involved in maximum glycogen breakdown in skeletal muscle
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Epinephrine signals cAMP cascade via beta-adrenergic receptors
Muscle only has b-adrenergic receptors Liver has alpha & beta -the stimulation of the veta and calcium together triggers optimal breakdown Calcium makes muscles contract and makes Phosphorylase kinase active and signals for glycogen breakdown |
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Explain how caffeine is able to improve human athletic performance
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Caffeine has the same affect as glucose on Phosphorylase
However its effects are seen in all tissues with glycogen It triggers for fat breakdown while sparing glycogen in muscle for later use |
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describe the mechanism of caffeine allowing for improved human athletic performance
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inhibits pohsophodiesterase to increase cAMP while also converting phosphorylase A to B (tense state)
increases FAT availability Decreases Carbohydrate stores Decreases threshold for motor unit recruitment INcreases ion transport within muscle INcrease catecholamine release |
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Glycogen storage disease
Von Gierke's Disease |
Most common glycogen storage disease
Type 1(a) mutation in Glucose-6-Phosphatase Symptoms: affects liver, enlarged liver, kidney failure diagnosed: liver/muscle biopsy treatment: limited to none |
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what causes glycogen storage diseases?
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mutations within the genes that may lead to excessive glycogen stores and therefor mal-effects
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Describe Von Gierke's Disease
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most common glycogen storage disease
Type 1 (a) mutation in Glucose-6-Phosphatase Symptoms: affects the liver, enlarged liver, kidney failure Diagnosed by liver/muscle biopsy |
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what type of mutation occurs in Von Gierkes disease?
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Type 1(a) mutation in Glucose-6-phosphatase
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describe Pompe's disease
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Type 2 mutation in Lysosomal Glucosidase
Symptoms: Skeletal and Cardiac muscle affected infantile form: death by 2 years juvenile form: muscle defects Adult form: muscular dystrophy diagnosis: muscle biopsy treat: enzyme replacement |
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what is McArdle's Syndrome
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Type 5 mutation in muscle phosphorylase
glycogen storage disease affects skeletal muscle exercise induced pain and cramps myoglobin present in urine diagnosis: muscle biopsy NO treatment |
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What is Cori's disease
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type 3(a) mutation in debranching enzyme
glycogen storage disease affects the liver and myopathy of muscles diagnosis: muscle or liver biopsy NO treatment |
