Biochem Spring Test 2

Front 1

Where is glycogen stored and why? How much energy as glycogen vs. serum glucose and
fats?

Back 1

-glycogen is stored in the liver and muscle
- serum glucose= 40kcal
-glycogen= 600kcal
-fat (100,000 kcal)

Front 2

Where does glycogen metabolism fit into the metabolic roadmap?

Back 2

-glycogen metabolism enters the metabolic roadmap at glucose 6- phosphate

Front 3

Know similarities and differences between breakdown and synthesis. How does the glycogen
phosphorylase reaction make glycogen a more energy-efficient storage form than it might
otherwise be?

Back 3

-glycogen breakdown includes using 4 enzymes, transferase and 1,6-glucosidase or debranching enzyme, glycogen phophatase, and mutase
-glycogen synthesis includes a UDP group and pyrophosphatase and glycogen synthase
-both are regulated by insulin release
-glycogen phosphatase adds a phosphate group to glycogen, making it a strong intermediate group for energy transfer

Front 4

How is glycogen synthesis and breakdown regulated? Hormone-initiated cascade? mechanisms involved?

Back 4

-glucagon acts on the liver to conduct glycogen breakdown by binding PP1 to phosphorylase a , eventually causing glycogen breakdown and inhiting synthase
-insulin acts for glycogen synthesis by binding PP1 the glycogen particle via the G subunit, glycogen iks dephosphorylated and synthase is activated
-adrenaline acts on muscles the same way as insulin by having PP1 bind to glycogen but phosphorylate them to activate glycogen phosphorylase

Front 5

What is the role of C-amp in regulating glycogen syntheis and breakdown?

Back 5

In the muscle
phosphorylase b can be partially activated by AMP (energy-poor indicator)
-In liver cells PP1 binds to phosphorylase a, which is present due to
the cAMP-mediated cascade of events initiated by glucagon.

Front 6

How does allosteric activation/deactivation of
phosphorylase b in muscle regulate glycogen synthesis/breakdown?

Back 6

In the muscle
phosphorylase b can be partially activated by AMP (energy-poor indicator) and this partially
activated form can be deactivated by ATP or Glucose 6-phosphate

Front 7

What is the allosteric effects of glucose in liver?

Back 7

-In liver cells glucose itself acts as the signal by allosterically converting phosphorylase a to b,
thereby releasing/activating PP1 which then inhibits breakdown and activates synthesis in a
manner identical to that in muscle cells.

Front 8

What is the roll of PP1 and insulin?

Back 8

-In muscle cells insulin activates PP1 by
promoting its binding to glycogen particles where PP1 then reverses breakdown and initiates
synthesis by removing the phosphate groups from both glycogen phosphorylase and synthase

Front 9

What are the differences between regulation in liver and muscle?

Back 9

-see book

Front 10

How is glycogen synthesis/breakdown regulated in the absence of hormones?

Back 10

-In the absence of hormone, allosteric activation of phosphorylase b by AMP -deactivation of the partially active phosphorylase b in ATP and glucose 6-phosphate
-increased activation
of synthase a by glucose 6-phosphate occurs only in muscle.

Front 11

How is breakdown/synthesis of glycogen regulated by hormones in the liver and muscle?

Back 11

-Epinephrine activates breakdown in muscle cells by binding to beta-adrenergic
receptors
-glucagon activates breakdown in liver cells (note that epinephrine also binds
to some extent to liver cells on both alpha and beta receptors.
-Binding to alpha receptors
involves Ca++ rather than cAMP as secondary messenger. Ca++ acts by stimulating
phosphorlyase kinase).

Front 12

What signals a stop to the hormone-induced breakdown of glycogen and how does the
“stop” signal differ in liver and muscle.

Back 12

in the liver, glucose stops glycogen breakdown
-in the muscle, insulin using PP1 to inhibit glycogen breakdown