Gluconeogenesis Flashcards Preview

Medical Biochemistry > Gluconeogenesis > Flashcards

Flashcards in Gluconeogenesis Deck (38):
1

where are most of the enzymes for gluconeogenesis?

cytosol

2

where is pryvate carboxylase found?

mitochondria

3

why is the mitochondria needed in gluconeogenesis?

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

4

Where is PEP carboxylase found?

mictochondria and cytosol

5

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

tight hormonal regulation

6

what are the irreversible steps of gluconeogenesis?

glucose 6-phosphatase

Fructose 1,6-bisphosphatase

pyruvate carboxylase
PEP carboxylase

7

where is glucose 6-phosphatase found

liver and kidney

8

where is glucose 6-phosphate generated?

gluconeogensis and glycogen degradation

9

what does glucogon activate at the same time?

gluconeogensis and glycogen degradation

10

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

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

11

when are liver glycogen levels remarkably reduced? totally depleted?

8 hours
24 hours fo fasting

12

where do lactate and alanine come from

muscle

13

how is lactate converted to pyrvuate?

using NAD+ to make NADH and use lactate dehydrogenase

14

how do you convert alanine to pyruvate ?

alpha KG + glutarate
alanine aminotransferase

15

what are the two enzymes needed for gluconeogenesis?

pyruvate carboxylase
PEP carboxylase

16

how is fructose 2,6 bisphosphate formed?

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

17

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

favored and gluconeogenesis is inhibited

18

what can the bifunctional enzyme do?

form fructose 2,6 bisP using PFK-2
degrade fructose 2,6-bisP using BPase

19

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

1 and 1

20

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

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

21

what does glucagon do to the bifunctional enzyme?

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

22

what is gluconeogenesis stimulated by?

glucagon and cortisol

23

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

blood glucose

24

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

hormonal control

25

what inhibits gluconeogenesis in the liver?

fructose 2,6 bisP

26

what substrates for gluconeogenesis are found in liver?

intermediates of glycolysis, lactate in the liver, glucogenic aa

27

what substrates for gluconeogenesis are found in the blood?

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

28

what are the energy requirements for gluconeogenesis?

2 pyruvate
4 ATP
2 GTP
2 NADH

29

how many nitrogen does alanine give to the liver?

1

30

how many nitrogen does glutamine give to the liver?

2

31

what is the advantage of the Cori cycle?

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

32

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

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

33

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

pyruvate is substrate for pyruvate carboxylase -- gluconeogenesis

34

what is the purpose of lactate in the heart?

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

35

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

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

36

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

alanine

37

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

glycerol released from fat cells after lipolysis of the stored TAGs

38

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

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