Lecture 303: gluconeogenesis Flashcards
1
Q
gluconeogenesis
A
- biosynthesis of glucose from non-carbohydrate substrates [pyruvate]
2
Q
g of glucose needed by entire body/ brain/ in storage
A
- body 160g
- brain needs 120g
- body has 210g glucose reserves
3
Q
where is glucose synthesized
A
- liver
- one precursor generated in mitochondria
- glucose generated in ER
- transported into cytosol [predominates here]
4
Q
3 irreversible steps of glycolysis bypassed during gluconeogenesis
A
- 2 enzymes needed for pyruvate kinase
- 1 enzyme needed for PFK-1
- 1 enzyme needed for hexokinase
5
Q
step 1
A
- bypassing pyruvate kinase
- done via pyruvate carboxylase and PEPCK
- pyruvate carboxylase REQUIRES ATP
- pyruvate carboxylase creates oxaloacetate in mitochondria = taken into cytosol via malate dehydrogenase
- PEPCK REQUIRES GTP AND IS REGULATED
- PEPCK acts in decarboxylation of oxaloacetate to PEP
6
Q
step 2
A
- PEP converted to F1,6BP via glycolytic enzymes
- entire energy investment here
7
Q
step 3
A
- bypass PFK-1 to convert F1,6BP to F6P via F1,6BPase
- most important step in gluconeogenesis
- regulated
- removes Pi group from C1
8
Q
step 4
A
- isomerize [synthesize] F6P to G6P via glycolytic enzymes
9
Q
step 5
A
- bypass glucokinase and hexokinase to convert G6P to glucose via G6Pase
- remove Pi group from C6
- in endoplasmic reticulum
10
Q
G6Pase found primarily
A
- liver
- kidney cortex
- organs that need glucose as primary carbon source DO NOT express G6Pase [can’t synthesize glucose]
11
Q
G6Pase deficiency
A
- Von Gierke Disease
- severe hypoglycemia
- enlarged liver
- growth failure, increased infection risk, impaired blood clotting, neurodevelopmental delay
12
Q
non-pyruvate starting points
A
- lactate, glutamine or alanine precursor to pyruvate
- glutamine or propionate precursor to oxaloacetate
- glycerol precursor to steps leading up to F1,6BP
13
Q
role of PEPCK in kidney cortex
A
- gluconeogenesis to detox ammonia
14
Q
role of PEPCK in adipose tissue
A
- adipose incapable of complete gluconeogenesis [lacks G6Pase]
- PEP produced by PEPCK converted to G3P [glyceroneogenesis]
- high levels of PEPCK leads to obese mice because of increased fat synthesis [inc. triacylglycerol content]
15
Q
role of PEPCK in skeletal muscle
A
- skeletal muscle incapable of complete gluconeogenesis [lacks G6Pase]
- PEPCK in high amounts led to freaky mice
