Chapter 14 ( Glycogen , Gluconeogenesis And HMS )

Question 1

Rate limiting enzyme of glycogen synthesis ?

Answer 1

Glycogen synthase

Question 2

Allosteric activator of glycogen phosphorylase and allosteric inhibitor ?

Answer 2

Activator : AMP , Ca
Inhibitor : ATP
In MUSCLES ONLY

Question 3

Rate limiting enzyme in glycogenolysis ?

Answer 3

Glycogen phosphorylase

Question 4

By which enzyme the only free glucose is produced directly in glycogenolysis ?

Answer 4

Debranching enzyme by the alpha-1,6 Glucosidase activity

Question 5

Von Gierke disease ?

Answer 5

Deficient enzyme : Glucose -6- phosphatase
Cardinal features : severe hypoglycemia, hepatomegaly, hyperlipidemia, lactic acidosis, hyperuricemia, short, doll like facies, protruding abdomen and emaciated extremities
Glycogen structure : normal

Question 6

Pomp disease ?

Answer 6

Deficient enzyme : lysosomal alpha1,4-glucosidase ( acid maltase )
Cardinal features : cardiomegaly
Muscle weakness
Death by 2 years
Glycogen structure : glycogen like material in inclusion bodies

Question 7

Cori disease ?

Answer 7

Deficient enzyme : debranching enzyme
Cardinal features : mild hypoglycemia and liver enlargement
Glycogen structure : short outer branches , single glucose residue at outer branch

Question 8

Andersen disease ?

Answer 8

Deficient enzyme : branching enzyme
Cardinal features : infantile hypotonia and cirrhosis
Death by 2 years
Glycogen structure : very few branches especially towards periphery (linear glycogen)

Question 9

McArdle disease ?

Answer 9

Deficient enzyme : muscle glycogen phosphorylase ( myophosphorylase )
Cardinal features : muscle cramps , weakness on exercise and myoglobinuria , recovery after 15 mins of exercise ( second wind )
Glycogen structure : normal

Question 10

Hers disease ?

Answer 10

Deficient enzyme : hepatic glycogen phosphorylase
Cardinal features : mild fasting hypoglycemia , hepatomegaly , cirrhosis
Glycogen structure : normal

Question 11

Cause of hyperuricemia in Von Gierke disease ?

Answer 11

Decreased Pi cause increased AMP which is degraded into uric acid , lactate slows uric acid excretion in the kidney

Question 12

When does gluconeogenesis represent the only source for glucose ?

Answer 12

After 24 hours of fasting

Question 13

Substrates for gluconeogenesis ?

Answer 13

Glycerol-3-phosphate
Lactate
Gluconeogenic amino acids

Question 14

Ketogenic and glucogenic amino acids ?

Answer 14

“PITTT”
Phenylalanine 
Isoleucine 
Tryptophan 
Threonine 
Tyrosine

Question 15

Requirements of Pyruvate carboxylase ? And its obligate activator

Answer 15

ABC
ATP
Biotin
CO2
Obligate activator : Acetyl-CoA

Question 16

The key control enzyme of gluconeogenesis ? Its activator and inhibitor ?

Answer 16

Fructose 1,6-bisphosphatase
Activator : ATP ( generated by fatty acid Beta oxidation )
Inhibitor : F2,6P

Question 17

Why can’t the skeletal muscle serve as source of blood glucose ?

Answer 17

Because of the absence of glucose-6-phosphatase in skeletal muscles

Question 18

Cori cycle ?

Answer 18

During fasting , Lactate from RBCs is converted in the liver to glucose that can be returned to RBCs or muscles

Question 19

Alanine cycle ?

Answer 19

Muscles release alanine drlivering both gluconeogenic substrate and an amino group for urea synthesis

Question 20

In alcoholism what does NADH favor ?

Answer 20

The formation of 
Lactate from pyruvate 
Malate from OAA in the cytoplasm
Glycerol-3-phosphate from DHAP
This effect divert important gluconeogenic structures from entering gluconeogenesis

Question 21

Inhibitor for alcohol dehydrogenase ?

Answer 21

Fomepizole

Question 22

Inhibitor of acetaldehyde dehydrogenase ?

Answer 22

Disulfiram

Question 23

Explain the presence of steatosis in alcoholism ?

Answer 23

Accumulation of NADH and glycerol-3phosphate contributes to lipid accumulation in alcoholic liver disease

Question 24

What are the major 2 functions of HMS ?

Answer 24

1- NADPH production

2- source for ribose-5-phosphate for nucleotide synthesis

Question 25

Rate limiting enzyme of HMS ? Its stimulator ? Inhibitor ? Activator ?

Answer 25

Glucose-6-phosphate dehydrogenase
Induced by : insulin
Inhibited by : NADPH
activated by : NADP

Question 26

The only thiamine enzyme in RBCs ?

Answer 26

Transketolase

Question 27

Functions of NADPH ?

Answer 27

Biosynthesis
Supply of reduced glutathione to protect against reactive oxygen species
Bactericidal activity in PMN

Question 28

Defect in Chronic Granulomatous Disease ( CGD ) ? Diagnostic test ? Patients susceptible to which organisms ?

Answer 28

NADPH oxidase is genetically deficient
Diagnostic test : Negative nitroblue tetrazolium test
Organisms : Catalase-positive organisms as S-aureus , E-coli , candida and aspergillus

Question 29

Defect in methemoglobinemia ? Its ttt ?

Answer 29

Met-Hb reductase is defective

Treated with Methylene Blue ( reductant )

Question 30

Glutathione structure ?

Answer 30

3 amino acids peptide with Cysteine in the middle

Question 31

Dangers of reactive oxygen species on RBCs ?

Answer 31

Hemoglobin may precipitate Heinz bodies

Membrane lipids may undergo peroxidation weakening the membrane and causing hemolysis

Question 32

How RBCs counter reactive oxygen species ?

Answer 32

By glutathione peroxidase/ glutathione reductase system which requires NADPH supplied by HMP shunt in RBCs

Question 33

Precipitators of hemolytic episodes in G6PD deficiency ?

Answer 33

Certain drugs
Fava beans
Overwhelming infections as pneumonia or infectious hepatitis

Question 34

When does symptoms of CGD develop in G6PD deficiency patients ?

Answer 34

If the G6PD activity is less than 5% of normal in PMN to generate NADPH for the NADPH oxidase bactericidal system