Gluconeogenesis is a pathway that generates glucose from non-carbohydrate carbon precursors such as pyruvate, lactate, glycerol, and certain amino acids.
Certain tissues, such as the brain and red blood cells, are absolutely dependent on glucose as their primary fuel. Ketone bodies aren't sufficient to provide the energy needs of these tissues. In the fasted state glycogen stores are sufficient to supply these tissue's requirement for glucose for approximately one day, so when the body is in the fasted state glucose must be formed from noncarbohydrate precursors, primarily lactate, certain amino acids, and glycerol. Gluconeogenesis is the pathway for converting noncarbohydrate precursors into glucose. The main routes of entry into gluconeogenesis are through pyruvate, oxaloacetate, or dihydroxyacetone phosphate. Most tissues do not have the ability to carry out gluconeogesis. Gluconeogenesis takes place mainly in the liver and to a lesser degree in the cortex of the kidney.
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Conceptual Vocabulary for Gluconeogenesis
Gluconeogenesis
Gluconeogenesis is the generation of glucose from non-sugar carbon substrates like pyruvate, lactate, glycerol, and glucogenic amino acids.
Hypoglycemia, also known as low blood sugar, is a fall in blood sugar to levels below normal.
Hyperglycemia is a condition in which an excessive amount of glucose circulates in the blood plasma.
A glucogenic amino acid is an amino acid that can be converted into glucose through gluconeogenesis.
Phosphoenolpyruvate carboxykinase is an enzyme in the lyase family used in the metabolic pathway of gluconeogenesis. It converts oxaloacetate into phosphoenolpyruvate and carbon dioxide.
Fructose bisphosphatase is an enzyme that converts fructose-1,6-bisphosphate to fructose 6-phosphate in gluconeogenesis and the Calvin cycle.
Glucose 6-phosphatase is an enzyme that hydrolyzes glucose 6-phosphate, resulting in the creation of a phosphate group and free glucose.
Pyruvate carboxylase is an enzyme of the ligase class that catalyzes the irreversible carboxylation of pyruvate to form oxaloacetate. Oxaloacetate can then either proceed to the citric acid cycle or to gluconeogenesis.
HMG-CoA reductase is the first enzyme of the mevalonate pathway that produces terpenes, terpenoids, steroids and various other biomolecules.
The Cahill cycle, also known as the alanine cycle, is the series of reactions in which amino groups and carbons from muscle are transported to the liver.
The Cori cycle refers to the cycling of lactate produced by red blood cells and muscle (during anaerobic respiration) back into glucose.
The alanine cycle is quite similar to the Cori cycle. When muscles produce lactate during times of decreased oxygen, they also produce alanine which is shuttled to the liver where it is used to make glucose.
Lactic acidosis is a medical condition characterized by the buildup of lactate (especially L-lactate) in the body,
Glycosuria is the excretion of glucose into the urine.
