Gluconeogenesis

Question 1

Gluconeogenesis is the

Answer 1

synthesis of glucose from non-carb precursors

• important for fasting/starvation
• liver and kidney help to main the glucose in the blood

Question 2

What are the precursors for gluconeogenesis?

Answer 2

1) Lactate (from skeletal muscle via lactic acid fermentation)
2) Amino acids (from proteins in diet vs starvation = breakdown of proteins in skeletal muscle)
3) Glycerol from triacylglycerols hydrolysis (may enter gluconeogenic or glucolytic pathway at DHAP)

Question 3

Pyruvate to phosphoenolpyruvate

Answer 3

Pyruvate + ATP + CO2 +H2O -> oxaloacetate +ADP + Pi + H+
enzyme: pyruvate carboxylase
Oxaloacetate +GTP -> phosphoenolpyruvate + GDP + CO2
enzyme: phosphoenolpyruvate carboxykinase

Question 4

Pyruvate to oxaloacetate requires:

Answer 4

Biotin (vit B7) - carrier of activated CO2, occurs in the mitochondria

Question 5

Need to get oxaloacetate from mitochondria to cytosol!!

Answer 5

Oxaloactate -> malate (which now passes through membrane to cytosol) -> oxaloacetate now in cytosol!

Question 6

Gluconeogenesis is the same as glycolysis from _____ to ______

Answer 6

Phosphoenolpyruvate to F-1,6-BP

Question 7

F-1,6-BP to F-6-P enzyme is:

Answer 7

fructose 1,6-biphosphatase

Question 8

F-6-P to G-6-P is

Answer 8

like in glycolysis

Question 9

G-6-P to glucose enzyme:

Answer 9

glucose 6-phosphatase

Question 10

In most tissues, gluconeogenesis ends with the formation of g-6-p because

Answer 10

there is a lack of glucose-6-phophatase, so instead make glycogen

Question 11

Gluconeogenesis and glycolysis regulation for f-6-p < > f-1,6-bp

Answer 11

1) energy is needed = high AMP
- glycolysis/PFK is activated by AMP and F-2,6-BP
- PFK is inhibited by citrate, H+, and ATP
2) Energy is high = high ATP and high citrate
- Gluconeogenesis/Fructose 1,6-biphosphatase is activated by citrate
- F-1,6-BP is inhibited by AMP amd F-2,6-BP

Question 12

In the liver, gluconeogenesis and glycolysis regulation

Answer 12

1) Energy is needed = high ADP
- F-1,6-BP activates pyruvate kinase
- ATP and Alanine inhibit pyruvate kinase
2) Energy is high = high ATP, alanine, and acetyl CoA
- ADP inhibits PEP carboxylase and pruvate carboxylase
- Acetyl CoA actives pyruvate carboxylase