Chapter 17- Gluconeogenesis Flashcards
What is gluconeogenesis?
In what does it exist?
Where is the site of it in animals?
Synthesis of new glucose from noncarbohydrate precursors
Exists in all animals plants fungi and microorganisms
In animals the site of gluconeogenesis is the liver, although it can occur in kidney as well (90-95% liver)
It is important during fasting or starvation, as glucose is primary fuel for the brain and only fuel for red blood cells
What are the precursors to gluconeogenesis for animals?
In microorganisms?
Lactate, pyruvate, glycerol, and most of the amino acids
In microorganisms, acetate, lactate, propionate are converted to glucose
In plants stored fats and proteins are converted into the disaccharide sucrose
How can gluconeogenesis be caused by reversing glycolysis?
Find some way to reverse the 3 enzymes of glycolysis (hexokinase, phosphofructokinase 1, and pyruvate kinase)
These can be reversed but not by the same enzyme, need a different one for each
Slide 3
How is pyruvate converted to phosphoenolpyruvate? (2 steps)
What are the enzymes for each step?
First starts with formation of oxaloacetate by pyruvate carboxylase (add carbon to pyruvate)
Then oxaloacetate is converted to phosphoenolpyruvate by phosphoenolpyruvate carboxylkinase
Slides 4 and 6
What is biotin?
What is it activated by?
Prosthetic group of carboxylase
All animal systems have carboxylase systems and have biotin as a prosthetic group
Requires ATP
Activated by acetyl CoA
How is pyruvate converted to oxaloacetate in the mitochondria?
2 reactions in mitochondria, 2 in cytosol
Pyruvate converts to oxaloacetate by atp and CO2
Oxaloacetate converts to malate by malate dehydrogenase
Malate is transported across membrane and once across cytosol it is converted back to oxaloacetate
Malate is major acid formed in apples and such, these acids are part of citric acid cycle and can be converted to energy quickly
Slide 7
How is L-malate converted to oxaloacetate?
What enzyme is used?
What’s the free energy released?
Slide 8
Malate dehydrogenase converts it
ΔG*’= 29.7 kJ/mol
How is fructose 1,6-biphosphate converted to fructose 6 phosphate and orthophosphate?
What enzyme does this?
Slide 9
Catalyzed by enzyme fructose 1,6-biphosphatase
Phosphatase are enzymes that remove the phosphate groups and produce a free phosphate
This is an irreversible step!
How is glucose 6-phosphate converted to glucose in the Er membrane?
Slide 10
Catalyzed by glucose 6 phosphatase in the membrane
Glucose 6 phosphatase is only present in the liver and kidney
How much energy is required to produce one molecule of glucose? (Potential test)
11 energy required
ATP- 4
GTP- 2
Energy- 11
Slide 11
How is Glycerol converted to glucose? (2 steps)
What enzymes catalyze these?
Glycerol is converted to glycerol phosphate by glycerol kinase
Glycerol phosphate is converted to dihydroxyacetone phosphate by glycerol phosphate dehydrogenase
This can be processed by gluconeogenesis or glycolysis
Slide 12
How can pyruvate be formed by lactate?
How are amino acids useful to gluconeogenesis?
Pyruvate can be formed by muscle derived lactate in the liver by lactate dehydrogenase
Carbon Skeletons of amino acids can be converted into gluconeogenic intermediates
Study slide 14 in depth. It is a review of everything from this chapter
Okay
What is the cori cycle
Glucose in liver can be transported to blood then transported anywhere in the body where needed
Gluconeogenesis in the liver
Glycolysis in the muscle
Slide 15
