42. Gluconeogenesis

Question 1

It is the process of synthesizing glucose from non-carbohydrate precursors, in order to prevent hypoglycemia during a fast

Answer 1

gluconeogenesis

Question 2

where does gluconeogenesis occur

Answer 2

liver - 90%
kidney - 10%
•mitochondria, cytosol

Question 3

substrate of gluconeogenesis

Answer 3

• intermediates of glycolysis and TCA
• glycerol and propionyl CoA from triacylglcerols
• Lactate through Cori cycle
• Carbon skeletons through glucogenic amino acids

Question 4

product of gluconeogenesis

Answer 4

glucose

Question 5

rate limiting step of gluconeogenesis

Answer 5

•Fructose 1,6 - biphosphate –> Fructose-6-phosphate

Enzyme: Fructose 1,6 - biphosphate

Question 6

the synthesis of 1 mole of glucose from 2 moles of lactate requires

___ moles of ATP

Answer 6

6 ATP

Question 7

steps of gluconeogenesis

Answer 7

1. Pyruvate -> oxaloacetate
   •(pyruvate carboxylase)
   •biotin, ATP
2. oxaloacetate -> malate or aspartate (to cytosol) -> oxaloacetate

CYTOSOL

3. oxaloacetate -> phosphoenolpyruvate 
•phosphoenolpyruvate carboxykinase 
•GTP 
4. PEP -> fructose 1,6-  biphosphate 
•reversal of glycolysis

5. fructose 1,6-biphosphate -> fructose-6- phosphate -> glucose-6-phosphate
   •fructose 1,6-biphosphatase
6. glucose-6-phosphate -> free glucose
   •glucose-6-phosphatase

Question 8

for oxaloacetate to cross mitochondrial membrane it is converted to

Answer 8

• aspartate

* malate

Question 9

attach a carbon atom using CO2 as a substrate

Answer 9

carboxlases

Question 10

carboxylases always require __ as a co-factor

Answer 10

biotin

Question 11

fructose-1,6-biphosphatase is inhibited by

Answer 11

• fructose-2,6,-biphosphate

* AMP

Question 12

final step of gluconeogenesis shared with glycogenolysis

Answer 12

Glucose-6-phosphate -> glucose

•glucose-6-phosphatase

Question 13

Net requirements to make 1 glucose

Answer 13

• 2 pyruvate
• 4 ATP
• 2 GTP
• 2 NADH
• 6 H2O

Question 14

gluconeogenesis is regulated by

Answer 14

• circulating levels of glucagon
• availability of glucogenic substrates
• allosteric activation of hepatic pyruvate carboxylase by acetyl CoA
• allosteric inhibition of fructose-1,6-biphospharase by AMP

Question 15

metabolic pathway in which lactate produced by anaerobic glycolysis in muscles is transported to the liver and glucose which returns to muscles
and is cyclically metabolized back to lactate

Answer 15

cori cycle

Question 16

energy requirement of gluconeogesis

Answer 16

6 high-energy phosphate bonds

2 NADH

Question 17

• when the glomerular filtate may contain more glucose than can be reabsorbed
• when blood glucose exceeds renal threshold 10.0 mmol/L

Answer 17

glucosuria

Question 18

hyperglycemia in critically ill patients is due to

Answer 18

excessive gluconeogenesis in response to injury and infection

associated with poor outcome

Question 19

hypoglycemia during pregnancy is due to

Answer 19

high fetal glucose consumption

Question 20

hypoglycemia in neonates

Answer 20

enzymes of gluconeogenesis are not fully developed

*premature and LBW infants are more susceptible - little adipose

Question 21

hypoglycemia in alcoholics

Answer 21

high amount of NADH is dformed by alcohol dehydrogenase and acetaldehyde dehydogenase

intermediates of gluconeogenesis are diverted to alternate rxn pathways -> dec glucose