Gluconeogenesis

Question 1

What is gluconeogenesis?

Answer 1

Synthesis of glucose from Noncarbohydrate substrates

Question 2

Glucose is the major source of fuel for

(6)

Answer 2

1. Brain
2. Nervous system
3. Erythrocytes
4. Testes
5. Renal Medulla
6. Embryonic tissues

Question 3

How long does Glycogen stores last without exogenous glucose?

Answer 3

Approximately 24 hours

Question 4

After overnight fast what are the values for Kidney/Liver function

Answer 4

90% Liver
10% Kidney

In prolonged starvation/hepatic failure-kidney increases to 40%

Question 5

What are the 4 gluconeogenic substrates?

Answer 5

1. Pyruvate-generated in muscle and other peripheral tissues (from transamination of alanine)
2. Lactate-tissues conducting anaerobic glycolysis-RBCs, no mitochondria or from tissues with low blood suppy-kidney medulla, lens, cornea
3. Amino Acids-catabolism of muscle proteins except (Leucine, Lysine)
4. Glycerol: from TAG hydrolysis in adipose tissue (via blood to liver and kidneys)

“the Losers” for amino acids

Question 6

Glycolysis vs Gluconeogensis

Answer 6

• Glucose catabolyzed/Glucose synthesized
• ATP is produced/ATP is consumed
• NAD+ is reduced to NADH/NADH is oxidized to NAD+

Gluconeogensis-anabolic

Question 7

What supplies energy for Gluconeogenesis?

Answer 7

Fatty acid oxidation in liver

Question 8

Bypass 1A of gluconeogenesis

Answer 8

Pyruvate to Oxaloacetate
Occurs exclusively to mitochondria

Question 9

Bypass 1B of gluconeogenesis

Answer 9

Oxaloacetate to Phosphoeneolpyruvate (PEP)
In mitochondria & cytosol

Question 10

Bypass 2 of gluconeogensis

Answer 10

Fructose-1,6-bisphosphate to Fructose-6-phosphate
Stimulated by ATP/irreversible

Question 11

Bypass 3 of gluconeogenesis

Answer 11

Glucose-6-phosphate to Glucose
Glucose-6-phosphate translocase transports G-6-Ptase into the endoplastmic reticulum where hydrolysis takes place

Not present in muscle

Question 12

Regulation of Glycolysis and Gluconeogenesis

Answer 12

One is inhibited when the other is active

Question 13

Effects of Glucagon

Answer 13

1. Favours gluconeogenesis over glycolysis
2. Increase transcription of the gene for PEP-carboxykinase

Question 14

Regulation of Gluconeogenesis by Substrate availability

Answer 14

Availability of gluconeogenic precursors
1. Lactate from RBC & exercising muscle
2. Amino acids released by cortisol or low insulin level, & in high protein/low CHO diet
3. Glycerol released when TAG is hydrolyzed in adipose tissue

Question 15

Cori Cycle

Lactate from Muscle

Answer 15

Lactate (NAD+toNADH)–>
Pyruvate–>Glucose (6ATP)

Question 16

Glycolysis and Gluconeogenesis Pathways

Answer 16