Glycogen

Question 1

Glycogen Linkages and Branching Formation

Answer 1

Linkages: Glycogen synthase creates alpha-(1,4) bonds between glycogen chain and UDP-glucose
Branches: alpha-(1,6 bonds)

Question 2

Glycogen Linkages and Breakages Breakdown

Answer 2

Linkages: Glycogen phosphorylase breaks down into G1P which can be converted to G6P, then glucose-6-phosphatase breaks down to glucose in liver and stuff. Muscles lack, so they use it for their own energy
Branches: Broken down directly into glucose so more efficient

Question 3

Glycogen Regulation

Answer 3

Stress (glucagon/epi): Rs stimulate AC/cAMP/PKA which activates glycogen phosphorylase kinase (activates glycogen phosphorylase) and inhibits glycogen synthase, so glycogen broken down
Insulin: Activates Glycogen synthase and protein phosphatase which inhibits glycogen phosphorylase, so make more glycogen

Question 4

Von Gierke Disease (Type I) (deficient enzyme, what it causes, lab findings)

Answer 4

Glucose 6 phosphatase, so get severe fasting hypoglycemia because can’t release glucose from liver in shit
Get elevated blood lactate/uric acid/hepatomegaly

Question 5

Pompe Disease (Type II) (deficient enzyme, what it causes)

Answer 5

Lysosomal alpha-1,4-glucosidase
Get cardiomegaly and shit in kids, leading to early death
In adults can have diaphragm problems

Question 6

Cori Disease (Type III) (deficiency, what it causes)

Answer 6

Debranching enzyme (alpha-1,6-glucosidase). So like milder form of Von Gierke/Type I with more mild fasting hypoglycemia and normal lactate levels

Question 7

McArdle Disease (Type V) (deficiency, what it causes)

Answer 7

Skeletal muscle glycogen phosphorylase, so increased glycogen in muscle but you can’t break it down. So painful muscle cramps until swelling and lysis, then myoglobin in serum and urine (red myoglobinuria)