Gluconeogenesis

Question 1

where are most of the enzymes for gluconeogenesis?

Answer 1

cytosol

Question 2

where is pryvate carboxylase found?

Answer 2

mitochondria

Question 3

why is the mitochondria needed in gluconeogenesis?

Answer 3

to use lactate, pyruvate and glucogenic aa as substrates for gluconeogenesis

Question 4

Where is PEP carboxylase found?

Answer 4

mictochondria and cytosol

Question 5

what ensures that glycolysis and gluconeogenesis won’t take place at the same time?

Answer 5

tight hormonal regulation

Question 6

what are the irreversible steps of gluconeogenesis?

Answer 6

glucose 6-phosphatase

Fructose 1,6-bisphosphatase

pyruvate carboxylase
PEP carboxylase

Question 7

where is glucose 6-phosphatase found

Answer 7

liver and kidney

Question 8

where is glucose 6-phosphate generated?

Answer 8

gluconeogensis and glycogen degradation

Question 9

what does glucogon activate at the same time?

Answer 9

gluconeogensis and glycogen degradation

Question 10

what two pathways provide blood glucose during the first day of fasting?

Answer 10

gluconeogensis and glycogen degradation (most used blood glucose at beginning of fast = branched structure)

Question 11

when are liver glycogen levels remarkably reduced? totally depleted?

Answer 11

8 hours

24 hours fo fasting

Question 12

where do lactate and alanine come from

Answer 12

muscle

Question 13

how is lactate converted to pyrvuate?

Answer 13

using NAD+ to make NADH and use lactate dehydrogenase

Question 14

how do you convert alanine to pyruvate ?

Answer 14

alpha KG + glutarate

alanine aminotransferase

Question 15

what are the two enzymes needed for gluconeogenesis?

Answer 15

pyruvate carboxylase

PEP carboxylase

Question 16

how is fructose 2,6 bisphosphate formed?

Answer 16

by the bifunctional enzyme when the insulin/glucagon ratio is high

Question 17

at high blood glucose levels, what happens to hepatic glycolysis?

Answer 17

favored and gluconeogenesis is inhibited

Question 18

what can the bifunctional enzyme do?

Answer 18

form fructose 2,6 bisP using PFK-2

degrade fructose 2,6-bisP using BPase

Question 19

how many proteins and how many genes does the bifunctional enzyme have?

Answer 19

1 and 1

Question 20

insulin leads to the dephosphroylation of bifunctional enzyme and does what?

Answer 20

form fructose 2,6-bisP = promotes glycolysis why? - PFK-2 is active

Question 21

what does glucagon do to the bifunctional enzyme?

Answer 21

phosphorylates it and degrades fructose 2,6 bisP and promotes gluconeogenesis –PFK-2 inactive!

Question 22

what is gluconeogenesis stimulated by?

Answer 22

glucagon and cortisol

Question 23

when liver glycogen stores are limited and once they are depleted, what is gluconeogenesis the sole provider for?

Answer 23

blood glucose

Question 24

why are glycogen degradation and glucoenogenesis going at the same time after eating? glucagon activate

Answer 24

hormonal control

Question 25

what inhibits gluconeogenesis in the liver?

Answer 25

fructose 2,6 bisP

Question 26

what substrates for gluconeogenesis are found in liver?

Answer 26

intermediates of glycolysis, lactate in the liver, glucogenic aa

Question 27

what substrates for gluconeogenesis are found in the blood?

Answer 27

new lactates from RBC and Cori cycle muscle alanine and glutamine (urea cycle) glycerol

Question 28

what are the energy requirements for gluconeogenesis?

Answer 28

2 pyruvate 4 ATP 2 GTP 2 NADH

Question 29

how many nitrogen does alanine give to the liver?

Answer 29

1

Question 30

how many nitrogen does glutamine give to the liver?

Answer 30

2

Question 31

what is the advantage of the Cori cycle?

Answer 31

allows for anerobic glycolysis in skeletal muscle and release of lactate into the blood without lactic acidosis because the lactate is used by the liver for gluconeogenesis

Question 32

what happens to pyruvate in the fed state when insulin is ruling?

Answer 32

its substrate for PDH and acetyl coA formation goes to TCA cycle

Question 33

what happens to pyruvate when glucagon is ruling in the fasting state?

Answer 33

pyruvate is substrate for pyruvate carboxylase -- gluconeogenesis

Question 34

what is the purpose of lactate in the heart?

Answer 34

pryruvate is formed and is substrate for the PDH and acetyl coA is used for energy metabolism big advantage - pyruvate is formed from lactate not glucose! - therefore blood glucose is saved

Question 35

since the heart always has enough ATP, what will be inhibited? why is this significant?

Answer 35

glycolysis and PFK-1 are inhibited by ATP this saves glucose heart perferes degrading fatty acids for energy - degradation of palmitate = 128 ATP!

Question 36

what specific aa can be used for gluconeogenesis and inhibits (at the same time) glycolysis in the liver at the PK level?

Answer 36

alanine

Question 37

what molecules is released during fasting into the blood and can be used donating carbon atoms for gluconeogenesis in the liver?

Answer 37

glycerol released from fat cells after lipolysis of the stored TAGs

Question 38

what substrates are mostly used for gluconeogenesis during starvation and where do they come from?

Answer 38

amino acids | low insulin levels and high cortisol levels leads to protein degradation in muscle -- they mainly alanine and glutaine