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Biochemistry FA > Glycogen > Flashcards

Glycogen Flashcards

0
Q

Glycogen-glucagon

Tissue?

A

Liver

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1
Q

Glycogen-epinephrine

Tissue

A

Liver and muscle

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2
Q

Glucogen-insulin

Tissue?

A

Liver and muscle

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3
Q

Protein responsible for glycogen synthesis

A

Glycogen synthase

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4
Q

Protein responsible for glycogen hydrolysis

A

Glycogen phosphorylase

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6
Q

Glucagon-glycogen pathway

A 
Glucagon receptor (LIVER) --> adenylate cyclase --> increased cAMP --> PROTEIN KINASE A --> glycogen phosphorylase kinase --> glycogen phosphorylase --> glycogen to glucose 
(Protein kinase A is a glycogen synthase inhibitor)
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7
Q

Epinephrin - glycogen pathway

A
  1. Epinephrin β receptor (liver or muscle) –> adenylate cyclase –> increased cAMP –> PROTEIN KINASE A –> glycogen phosphorylase kinase –> glycogen phosphorylase –> glycogen to glucose (Protein kinase A is a glycogen synthase inhibitor)
  2. Epinephrin α receptor (LIVER) –> increased calcium from endoplasmic reticulum. Calcium can activate glycogen phosphorylase kinase :
  3. Directly
  4. Via calcium-calmodulin in muscle during contraction
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8
Q

Alternative epinephrin glycogen pathway

A

Epinephrin α receptor (LIVER) –> increased calcium from endoplasmic reticulum. Calcium can activate glycogen phosphorylase kinase :

  1. Directly
  2. Via calcium-calmodulin in muscle vis contraction
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9
Q

Insulin action on glycogen synthesis

A

Tyrosine kinase dimer receptor (liver + muscle)

  • inhibits glycogen phosphorylase via protein phosphatase
  • induce glycogen synthase (directly or via protein phosphatase)
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9
Q

Insulin action on glycogen synthesis inhibits glycogen phosphorylase via

A

Tyrosine kinase dimer receptor (liver + muscle)

  • inhibits glycogen phosphorylase via protein phosphatase
  • induce glycogen synthase
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10
Q

Glucagon and epinephrin inhibit glycogen synthesis via

A

Protein kinase A is a glycogen synthase inhibitor

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11
Q

Glycogen bonds

A

a-(1,6) bonds

a-(1,4) bonds

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12
Q

Glycogen in skeletal muscles

A

It undergoes glycogenolysis to glucose-1-P –>glucose 6-P which is rabidly metabolized during exercise

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13
Q

Glycogen bonds

A

branches: a-(1,6) bonds
linkages: a-(1,4) bonds

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14
Q

Glycogen in hepatocytes function

A
  1. Storage

2. Glycogenolysis to maintain blood sugar at appropriate levels

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15
Q

Glycogen phosphorylase

A

Cleaves glucose-1-P residues off branched glycogen until four remain before a branch point

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16
Q

Glycogen enzymes

A
  1. UDP-glucose pyrophosphorylase
  2. Glycogen synthase
  3. Branching enzyme
  4. Glycogen phosphorylase
  5. 4-a-D-glucanotransferase (debranching enzymes)
  6. a-1,6-glucosidase (debranching enzymes)
  7. α-1,4-glucosidase
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17
Q

Glycogen building block

A

UDP-glucose

18
Q

UDP-glucose pyphosphorylase function

A

Glucose -1-P to UDP-glucose (to be ready for glycogen formation)

20
Q

glycogen - Branching enzymes - function and types

A

Makes linear glycogen

  • 4-a-D-glucanotransferase
  • a-1,6-glucosidase
20
Q

a-1-6-glucosidase function

A

Cleaves off the last glucose 1-P on the branch

21
Q

4-a-D-glucanotransferase function

A

Moves 3 glucose-Ps from the brunch to the linkage (leaves 1)

22
Q

Acid maltase

A

A small amount of glycogen is degraded in in lysosomes by a-1,4-glycosidase

23
Q

Limit dextrin

A

One to four residues remaining on a branch after glycogen phosphorylase has already shortened it

24
Q

Glycogen storage diseases

How many tyoes

A

12 types all resulting in abnormal glycogen metabolism and accumulation of glycogen within cells

26
Q

Glycogen storage disease type 1 / mode of inheritance

A

Von Gierke disease AR

27
Q

Glycogen storage disease type 2 / mode of inheritance

A

Pompe disease AR

28
Q

Glycogen storage disease type 3 / mode of inheritance

A

Cori disease AR

28
Q

Mode of inheritance of glycogen storage diseases type 1-4

A

AR

29
Q

Glycogen storage disease type 4 / mode of inheritance

A

McArble disease AR

31
Q

Von Gierke disease (type 1) pathophysiology

A

Glucose-6-phosphatase deficiency –> impaired gluconeogenesis and glycogenolysis

32
Q

Von Gierke disease (type 1) findings

A
  1. Severe fasting hypoglycemia
  2. Increased glycogen in liver
  3. Increased blood lactate
  4. Hepatomegaly
  5. incdreased TG
  6. increased Uric acid (Gout)
33
Q

Von Gierke disease (type 1) treatment

A

Frequent oral glucose/cornstarch

Avoidance of fructose and galactose

34
Q

Pompe disease (type 2) pathophysiology

A

lysosomal a-1,4-glucosidase with α-1,4-glycosidase activity (Acid maltase) deficiency

34
Q

Pompe disease (type 2) findings

A
  1. Cardiomyopathy
  2. hypertrophic cardiomyopathy
  3. exercise intolerance
  4. Systemic findings leading to early death
35
Q

Pompe disease (type 2) findings

A
  1. Cardiomegaly
  2. hypertrophic cardiomyopathy
  3. exercise intolerance
  4. Systemic findings leading to early death
37
Q

Cori disease (type 3) pathophysiology

A

a-1,6-glucosidase deficiency

37
Q

McArdle disease (type 4) pathophysiology

A

Skeletal muscle phosphorylase (myophosphorylase deficiency)

38
Q

Cori disease (type 3) findings

A
  • Milder form of type 1 with normal blood lactate (and gluconeogenesis is intact)
  • Accumulation of limit dextrin-like structures in cytosol
40
Q

McArdle disease (type 4) findings / mechanism

A
  1. Increased glycogen in muscle, but cannot break it down leading to painful muscle cramps
  2. Myoglobinuria (red urine) with strenuous exercise
  3. Arrythmia from electrolyte abnormalities
  4. 2nd wind phenomenon noted during exercise due to increased muscular blood flow
41
Q

There any problem with gluconeogenesis in Cori disease?

A

No. It is intact

42
Q

It is useful for Glycogen storage disease diagnosis

A

Periodic acid-Schiff stain

43
Q

Skeletal muscle phosphorylase

A

Myophosphorylase

44
Q

blood glucose in McArdle disease

A

unaffected

Biochemistry FA (16 decks)

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