Gluconeogensis

Question 1

why is gluconeogenesis important?

Answer 1

helps the body maintain glucose levels during fasting

Question 2

what does gluconeogenesis use to make glucose?

Answer 2

amino acids, lactate, and glycerol

Question 3

where does gluconeogenesis occur?

Answer 3

mainly the liver (could also be epithelial cells in kidney or intestine

Question 4

Fasting, where do we get glucose?

Answer 4

1) glycogen stores (12-24 hours) until we run out

2) gluconeogenesis (kicks in 12 hrs in as main provider of glucose)

Question 5

gluconeogenesis

Answer 5

uses ATP to turn pyruvate into glucose

Question 6

which glycolysis reactions are irreversible?

Answer 6

1, 3, and 10

Question 7

sources of pyruvate for gluconeogenesis (1)

Answer 7

lactate (lactate dehydrogenase takes Hydrogen from lactate and makes it pyruvate while making NADH)

Question 8

sources of pyruvate for gluconeogenesis (2)

Answer 8

amino acids (alanine)
alanine comes from breakdown of protein and skeletal muscle cells
alanine transaminase (vitamin B6 as a cofactor) removes amino from alanine and turns it to pyruvate

Question 9

during fasting,

Answer 9

pancreas senses low glucose, releases glucagon

there is also low insulin, high epinephrine

Question 10

gluconeogenesis step 1A

Answer 10

1) pyruvate enters mitochondria

2) pyruvate carboxylase adds a carbon to it creating oxaloacetate

Question 11

carboxylase enzymes require what cofactors

Answer 11

ABC
ATP
Biotin
CO2

Question 12

gluconeogenesis step 1B

Answer 12

• we need oxaloacetate out of mitochondria and into the cytoplasm
  1) malate dehydrogenase adds Hydrogen to oxaloacetate making malate
  2) malate can exit mitochondria and get into cytoplasm where malate dehydrogenase converts it back into oxaloacetate

Question 13

gluconeogenesis step 1C

Answer 13

oxaloacetate to phosphoenolpyruvate

enzyme: PEPCK removes a carbon and adds a phosphate
requires GTP

Question 14

PEPCK regulation

Answer 14

stress hormones: glucagon, epinephrine, and cortisol enhance PEPCK by induction

Question 15

gluconeogenesis 2nd roadblock

Answer 15

PEP to DHAP

Question 16

using glycerol

Answer 16

• glycerol can make DHAP
• glycerol kinase adds phosphate from ATP to C3 on glycerol
• makes glycerol-3-phosphate (G3P)
• glycerol-3-phosphate dehydrogenase converts G3P to DHAP

Question 17

gluconeogenesis 3rd roadblock

Answer 17

PFK1 rxn

in gluconeogenesis, fructose 1,6 bisphosphatase removes phosphate from C1 of fructose-1,6-bisphosphate making fructose-6-phosphate

Question 18

rate limiting step of gluconeogenesis

Answer 18

fructose-1,6-bisphoshatase

Question 19

up-regulation of gluconeogenesis

Answer 19

when liver burns a lot of fat making a lot of ATP

high ATP = enhances fructose-1,6-bisphosphatase

Question 20

fructose-1,6-bisphosphatase regulation

Answer 20

glucagon activates, insulin inhibits

Question 21

final step of gluconeogenesis

Answer 21

glucose-6-phosphate to glucose

enzyme: glucose-6-phosphatase
- once phosphate is removed, glucose can enter bloodstream

Question 22

high levels of alcohol (ethanol)

Answer 22

• processed in liver

- cause increase in NADH and ATP

Question 23

high NADH causes

Answer 23

lactate, malate, and G3P dehydrogenase enzymes in gluconeogenesis to go the reverse way

impairs gluconeogenesis!
causes low blood sugar when fasting