L12: Gluneogenesis Flashcards Preview

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Flashcards in L12: Gluneogenesis Deck (39)
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1
Q

where does gluconeogenesis occur?

A
  • in mitochondrion and cytoplasm

- generally occurs in the liver under fasting conditions

2
Q

why use gluconeogenesis?

A
  • glucose levels needs to be maintained since the brain uses glucose for fuel
  • mostly used by brain, muscle, and red blood cells
3
Q

Noncarbohydrate precursors that generate pyruvate

A
  • lactate
  • amino acids
  • glycerol - breakdown of fat
4
Q

fed state:

A
  • dietary glucose is exhausted quickly

- just after a meal, the glucose you consumed is depleted after a few hours

5
Q

fasting state

A
  • breakdown of glycogen to glucose
  • lactate, amino acids, and glycerol will come in and help generate glucose
  • when you need a boost of energy
  • goes away after about a day
6
Q

starved state

A
  • gluconeogenesis provides a relatively constant level of glucose
  • provided by the liver
7
Q

where does glycerol come from?

A
  • released from fat stores (adipose cells) due to triglyceride breakdown
8
Q

where does propionate come from?

A
  • odd-chain fatty acids

- produce propiony-CoA

9
Q

propionyl-CoA track

A
  • propionyl CoA -> succinyl CoA -> TCA cycle -> oxaloacetate
10
Q

which is the major gluconeogenic amino acid?

A
  • alanine
11
Q

lactate comes from?

A
  • muscle tissues undergoing anaerobic glycolysis

- through circulation and enters liver

12
Q

lactate to pyruvate

A
  • requires lactate dehydrogenase

- requires NAD+

13
Q

When NADH levels are high?

A
  • reaction goes toward lactate

- inhibits gluconeogenesis

14
Q

alanine to pyruvate

A
  • via alanine aminotransferase
15
Q

glycerol to DHAP

A
  • glycerol -> glycerol-3-phosphate by glycerol kinase

- glycerol-3-phosphate -> DHAP by glycerol-3-phosphate dehydrogenase

16
Q

unique reaction 1 of gluconeogenesis

A
  • pyruvate -> oxaloacetate
  • via pyruvate carboxylase and ATP
  • also requires biotin and CO2
  • reaction occurs in the membrane
17
Q

oxaloacetate transport

A
  • oxaloacetate is converted to malate and exits mitochondria
    • cannot cross mitochondrial membrane on its own
  • malate is transported to cytoplasm
  • malate is converted back to oxaloacetate
18
Q

oxaloacetate phosphorylation

A
  • oxaloacetate -> phosphoenolpyruvate
  • via phosphoenolpyruvatecarboxykinase
  • requires GTP
19
Q

how to form fructose-6-phosphate from fructose-1,6-bisphosphate

A
  • uses fructose-1,6-bisphosphatase
20
Q

form glucose from glucose-6-phosphate

A
  • uses glucose-6-phosphatase
  • found in liver and kidney to transport to other tissues
  • occurs in the ER
    • glucose-6-phosphate transported into ER lumen
    • glucose transported back to the cytoplasm
21
Q

which is the most preferred end product?

A
  • glucose-6-phosphate

- because it cannot be transported out of the cell like glucose

22
Q

how much energy is required for gluconeogenesis?

A
  • 4 ATP
  • 2 GTP
  • 2 NADH
23
Q

when is glycolysis favored?

A
  • when energy is needed

- glycolytic intermediates are needed for biosynthesis

24
Q

when is gluconeogenesis favored?

A
  • when energy is abundant

- when glucose precursors are abundant

25
Q

pyruvate carboxylase regulation

A
  • pyruvate -> oxaloacetate
  • stimulated by acetyl CoA
  • inhibited by ADP
26
Q

phosphoenolpyruvate carboxykinase regulation

A
  • oxaloacetate -> phosphoenolpyruvate

- inhibited by ADP

27
Q

pyruvate dehydrogenase inhibited by

A
  • acetyl CoA

- NADH

28
Q

pyruvate dehydrogenase stimulated by

A
  • ADP
29
Q

pyruvate kinase inhibited by

A
  • PEP - pyruvate
  • ATP
  • Alanine
  • glucagon signaling
30
Q

fructose-1,6-bisphosphatase regulation

A
  • activated by citrate

- inhibited by AMP and F-2,6-BP

31
Q

PFK-1 regulation

A
  • inhibited by ATP, citrate, and H+

- activated by F-2,6-BP and AMP

32
Q

If F-2,6-BP levels are high

A
  • indicates high glucose levels

- you want to break down glucose

33
Q

low glucose results in

A
  • release of glucagon
34
Q

glucagon stimulates

A
  • cAMP cascade

- activates PKA

35
Q

PKA role in gluconeogenesis

A
  • phosphorylation PFK2 Kinase domain

- activation of PBPase2

36
Q

PBPase role

A
  • reduces F-2,6-BP levels and increase levels of F-6-P

- No PFK stimulation

37
Q

glucagon signaling also does what

A
  • increases transcription of genes that encode enzymes that carry out gluconeogenesis
  • inhibits expression of glycolytic enzyme genes
38
Q

when glucose is high

A
  • insulin activates phosphoprotein phosphatase
  • removes phosphate from and activates PFK2
  • increases F-2,6-BP from F-6-P
    • stimulates PFK
  • glycolysis predominates
39
Q

glucokinase

A
  • same role as hexokinase (present in all other body tissues)
  • only in the liver
  • high Km