Glycogenesis, Glycogenolysis, Gluconeogenesis

2 enzymes that convert glucose to G6P and location

• Hexokinase (Muscle)

• Glucokinase (Liver)

Hexokinase can be _____ by G6P

inhibited

Glucokinase is NOT inhibited which is why glycogen storage is mainly in the _____

liver (3-5% tissue mass)

Glycogenesis steps:

1. Glucose → G6P → G1P →UDP

2. glycogen primer

3. Glycogen synthase can link UDP to primer → a1-4chain

4. a1-4chain → a1-6 chain

Glycogenesis enzymes (3)

1. Glycogen phosphorylase

2. Transglucosylase

3. Glucan transferase

Glycogenolysis

Glycogen to Glucose

Glycogenolysis steps

1. Glycogen phosphorylase catalyzes cleaveage of a1-4 linkage of glycogen

2. Debranching enzymes cleaves a1-6 linkage of glycogen to remove branches

3. G1P to G6P by phosphoglucomutase

Glycogenolysis Regulation Insulin

• Promote glucose storage/glycogen synthase

• Inhibit Glycogenolysis

Glycogenolysis regulation Glucagon

Activate glycogenolysis, glycogen phosphorylase

Inhibit glycogen synthase

Glycogenolysis regulation Epinephrine

Activate glycogenolysis

Glycogenolysis is ______ by demand for blood glucose

activated

Glucagon is secreted from a-cells of the _____

pancreas

Glucagon cascade steps

1. Glucagon PM R is activated by GDP/ADP

2. adenylate cyclase converts ATP to cAMP

3. cAMP cascades to glucose generation

Gluconeogenesis is when we run out of C-stores and have to make ____ from other C-sources

glucose

Gluconeogenesis occurs mostly in the

Liver

Gluconeogenesis requires (2)

• Energy source (metabolism of FA)

• Carbon soource (lactate/acetylCoA/AA/Glycerol)

Gluconeogenesis steps

Lactate or Acetyl CoA → Pyruvate (cannot pass PM) → OAA (cannot pass PM) → malate (can pass PM) → OAA → PEP → 2PG → 3PG → 1,3-biphosphoglycerate → G3P → Fructose 1,6-biphosphate → F6P

Fructose 1,6-biphosphate → F6P is irreversible in glycolysis so instead we use

FBPase-1

F2,6-BP (activates/inhibits) PFK1 (glycolysis)

activates

F2,6-BP (activates/inhibits) FBPase (gluconeogenesis)

inhibits

Gluconeogenesis is a(n) (anabolic/catabolic) mechanism

anabolic

Gluconeogenesis input and importance

• 4 ATP

• 2 NADH

• 2 GTP

requires more energy input to go “uphill“, since glycolysis is downhill, their difference in energy drives gluconeogenesis

Gluconeogenesis regulatory steps:

1. Pyruvate carboxylase coverts pyruvate to OAA

2. Pyruvate dehydrogenase catalyzes pyruvate to acetyl CoA (regulated)

3. F1,6BP is dephosphorylated to F6P by FBPase-1

PFK-1 is (activated/inhibited) by AMP (F6P → F1,6-BP ) (glycolysis)

activated

FBPase-1 is (activated/inhibited) by AMP (F1,6-BP → F6P) (gluconeogenesis)

inhibited

The Cori Cycle is when

• NAD+ is replenished when aerobic respiration is too slow/being overexerted

• Final electron acceptor other than O2

Cori Cycle input:

• Pyruvate

• NADH

Cori Cycle output:

• Lactate

• NAD+

Cori Cycle definition

combo of glucose transport to active tissues and reverse transport of lactate from those tissues back to the liver to sustain glucose levels

The cori cycle occurs in the…

muscles and liver

Cori Cycle muscle pathway

Glucose → Pyruvate → lactate → blood (glycolysis)

Cori Cycle Liver pathway

Blood → lactate → pyruvate → glucose (gluconeogenesis) → reenter muscle