W5- Lecture 19- Gluconeogenesis

Question 1

where does Gluconeogenesis mainly occur ?

Answer 1

in the liver

Question 2

what is the aim of Gluconeogenesis ?

Answer 2

Formation of glucose from non-carbohydrate sources

Question 3

how many steps does Gluconeogenesis contain ?

how many a reversible ?

Answer 3

3

0

Question 4

Name the Gluconeogenic substrates(5)

Answer 4

Amino acids (not leucine or lysine)

Lactate

Pyruvate

Glycerol (from stored fats)

Oxaloacetate

Question 5

where is glycerol derived from ?

Answer 5

triglyceride breakdown

Question 6

explain the conversion of pyruvate to Oxaloacetate (1st)

Answer 6

pyruvate +HCO3- +ATP
catalysed by Pyruvate carboxylase which is biotin bound
ADP +PI

Question 7

Explain the conversion of Oxaloacetate to Phosphenolpyruvate

Answer 7

Oxaloacetate +GTP
Catalysed by Phosphoenolpyruvate carboxykinsae
Phosphenolpyruvate +GDP + CO2

Question 8

Pyruvate carboxylase
where is it found ?
purpose/ why
mechanism depends on

Answer 8

in the mitochondria
to transport Oxaloacetate out of mitochondria into cytosol as most gluconeogenic enzymes are found in the mitochondria
depends on degeneration of NADH for use in Glyceraldehyde-3-phosphate dehydrogenase catalysed reaction

Question 9

explain the movement of Pyruvate+ (itself modified) to conversion of PEP
under normal conditions

Answer 9

Pyruvate transported into mitochondria
Converted to oxaloacetate
Reduced to malate and export to cytosol (NADH use)
Malate dehydrogenase oxidises malate to oxaloacetate (NADH use)
Oxaloacetate converted to PEP

Question 10

how is the movement of Pyruvate+ (itself modified) to conversion of PEP different in vigorous exercise stress conditions

Answer 10

Lactate converted to pyruvate – regenerates NADH for use in GAPDH reaction

Conversion of pyruvate to PEP occurs in mitochondria

PEP exported to cytosol

Question 11

why cant organs and tissues convert lactate to glucose?

where can this be done ?

Answer 11

Glycolysis is found in almost all cell types in body,Gluconeogenesis occurs primarily in liver.

liver

Question 12

what is the energy cost in the cori cycle

lactate to glucose

Answer 12

– net 2 ATP produced in anaerobic glycolysis
– 4 ATP and 2 GTP used in gluconeogenesis
=net 4 ATP (equivalents) used(6-2)

Question 13

what are the benefits of the cori cycle (lactate to glucose)

Answer 13

Rapid replenishment of glycogen stores post exercise

Regeneration of NAD+ for glycolysis and NADH for gluconeogenesis happen in different tissues

Question 14

do we need to know the big ass diagram ?

Answer 14

maybe