Chapter #17: Gluconeogensis Flashcards
What is the postprandial state?
Following a carbohydrate-containing meal, glucose is absorbed from the intestines for roughly 2 to 3 hours, and once that source is depleted, glucose must be maintained from glycogen.
This period is termed the postprandial (after eating) state.
What is the post absorptive state?
During the period of plentiful glucose from the diet, glycogen is synthesized in the liver. As glucose levels in the blood decline, glycogen is the first energy store used. About four hours after a meal, glycogen begins to be broken down to be converted again to glucose. For the next 8–12 hours, glucose derived from liver glycogen will be the primary source of blood glucose to be used by the rest of the body for fuel.
This period is termed the post absorptive state.
What is the fasting state?
Most tissues can use fats as a source of energy when glycogen stores are depleted, but glucose is still required by the brain and red blood cells. After about 12 hours, when glycogen reserves are depleted, the liver shifts to making glucose from other sources (amino acids, lactate, glycerol) by the process of gluconeogenesis, which is essential for surviving fasting or starvation.
Beyond post absorptive is the fasting state.
What is gluconeogenesis?
- Synthesis of glucose from three main non-carbohydrate precursors:
- Lactate
- Amino acids
- Glycerol
- Primary location = liver
- Costs 6 ATP/molecule of glucose - why run gluconeogenesis?
- Isn’t simply a reversal of glycolysis – why?
How do we get past these irreversible steps to make glucose?
Describe the overall steps of gluconeogenesis?
What is the cost of gluconeogenesis?
What’s the result of running glycolysis and gluconeogenesis simultaneously?
What is the G-6P regulation of glycolysis and gluconeogenesis?
What is the ATP regulation of glycolysis and gluconeogenesis?
What is the AMP regulation of glycolysis and gluconeogenesis?
What is the pH regulation of glycolysis and gluconeogenesis?
What is the F-2,6-BP regulation of glycolysis and gluconeogenesis?
Fructose 2,6-bisphosphate is a strong regulator of phosphofructokinase (positive) and fructose 1,6 bisphosphatase (negative).
What is the citrate regulation of glycolysis and gluconeogenesis?
What is the alanine regulation of glycolysis and gluconeogenesis?
What is the F-1,6-BP regulation of glycolysis and gluconeogenesis?
What is the ADP regulation of glycolysis and gluconeogenesis?
What is the Acetyl CoA regulation of glycolysis and gluconeogenesis?
This regulation is a link between gluconeogenesis and the process of fatty acid oxidation (fatty acid breakdown). The presence of acetyl CoA coordinates the gluconeogenic process and it’s required energy supply.
Go into greater depth of gluconeogenesis regulation by F-2,6-BP
What is the take home message of gluconeogenesis
- The gluconeogenesis pathway is not the reverse of glycolysis.
- Gluconeogenesis can use various precursors to generate glucose.
- Glycolysis and gluconeogenesis are reciprocally reversed to avoid a futile cycle.
How to study gluconeogenesis?
