10/2 Gluconeogenesis

Question 1

effect of phosphorylation of glycogen synthase

Answer 1

deactivation (multiple pathways to do this)

Question 2

effect of phosphorylation of glycogen phosphorylase

Answer 2

activation

Question 3

precursors for gluconeogenesis

Answer 3

lactate, pyruvate, glycerol, amino acids, and any Krebs intermediate that can form oxaloacetate

Question 4

source of glycerol for gluconeogenesis

Answer 4

from lipolysis of triglycerides in adipose tissue

Question 5

hormonal effect of drop in blood [glucose]

Answer 5

(fasted state)
glucagon is dominant hormone

increases: glycogenolysis, gluconeogenesis, lipolysis (goal: make energy available)
decreases: liver glycolysis

Question 6

hormonal effect of rise in blood [glucose]

Answer 6

(fed state)
insulin is dominant hormone

increases: glycogenesis, fatty acid synthesis, triglyceride systhesis, liver glycolysis (goal: store energy)

Question 7

role of FA oxidation in gluconeogenesis

Answer 7

mitochondrial fatty acid oxidation produces the energy needed to drive gluconeogenesis (ATP, GTP, NADH)

lactate can also be the source of these through its conversion to pyruvate

Question 8

how is glycogenolysis triggered in mm?

Answer 8

when ATP in skel mm is low, triggered

NO receptors for glucagon, so no diff btwn fed/fasted state

skel m lacks glucose 6-phosphatase (G6P–>glucose), so G6P is committed to glycolysis

Question 9

m glycogen phosphorylase

Answer 9

chain degredation
Pi = activation
(+) AMP (but not in liver cells)
glucose does NOT inhibit it

Question 10

m glycogen synthase

Answer 10

chain elongation
Pi = inactivation
(-) glycogen

Question 11

source of lactate for gluconeogenesis

Answer 11

muscle and RBC glycolysis

Question 12

source of amino acids for gluconeogenesis

Answer 12

alanine

from glycolysis and amino acid metabolism

Question 13

source of pyruvate for gluconeogenesis

Answer 13

AAs, alanine, and lactate are converted into pyruvate, which is then converted into oxaloacetate

Question 14

when does gluconeogenesis occur?

Answer 14

fasting, stress, high protein diet, prolonged exercise

Question 15

two effects of Acetyl-CoA

Answer 15

activates pyruvate carboxylase

inhibits pyruvate dehydrogenase

Question 16

what energy is required per one glucose molecule synthesized through gluconeogenesis

Answer 16

4 ATP, 2 GTP, 2 NADH

Question 17

role of liver in maintaining blood [glucose]

Answer 17

in a fasted state, the liver’s gluconeogenesis is the only source of glucose. essential b/c the brain and RBCs require glucose but cannot synthesize their own. prevents hypoglycemia

Question 18

four irreversible enzymes of glycolysis

Answer 18

glucokinase
phosphofructokinase-1
pyruvate kinase
pyruvate dehydrogenase

Question 19

four enzymes of gluconeogenesis that circumvent (glycolysis’ irreversible enzymes)

Answer 19

pyruvate carboxykinase (pyruvate dehydrogenase)
phosphoenolpyruvate carboxykinase (pyruvate kinase)
fructose 1,6-bisphosphatase (phosphofructokinase-1)
glucose 6-phosphatase (glucokinase)

Question 20

pyruvate carboxykinase (PC)

Answer 20

replaces pyruvate dehydrogenase
in mitochondria in fed and fasted state

pyruvate —> oxaloacetate
requires ATP and biotin

Question 21

phosphoenolpyruvate carboxykinase (PEPCK)

Answer 21

replaces pyruvate kinase
in cytosol and mitochondria (isoforms)

oxaloacetate —> phosphoenolpyruvate
requires GTP

Question 22

fructose 1,6-bisphosphatase (FBPase-1)

Answer 22

replaces phosphofructokinase-1
in cytosol
(+) low blood [glucose]

fructose 1,6-bisphosphate —> fructose 6-phosphate

Question 23

glucose 6-phosphatase (G6Pase)

Answer 23

replaces glucokinase
in ER

glucose 6-phosphate –> glucose

T1: G6P into ER
T2: Pi into cytosol
T3: glucose into cytosol