GLUCOGENESIS. SUBSTRATE CYCLES
* Introduction. Glycogenesis is the opposite route to glycolysis, although it does not coincide in all respects with it, since many enzymes of the glycolysis enzymes are bidirectional and also catalyze steps of gluconeogenesis. This is a route that helps us get energy during long fasts or after vigorous exercise.
> Postprandial state. When we eat food, glucose levels rise. To maintain normoglycemia, excess glucose is stored as glycogen. This normoglycemia is achieved 2 hours after ingestion.
To maintain this normoglycemia, glucose will travel to the different organs of the body so that they use it and can generate energy from it or it will be stored in the liver in the form of glycogen.
It should be noted that there are organs, such as the muscle, that have their own glucose reserves, while others need an almost constant supply of it.
> Fasting state. In fasting situations, blood glucose levels decrease, producing hypoglycemia, which is important to correct, since the organs depend on the supply of glucose.
In this situation, glucose is obtained from glycogen stores Glicerol stored in the liver, which take about 10 hours to run out. The regions that op not perform gluconeogenesis and that need a constant Cerebro y tejido nervioso supply of glucose are the brain, the muscle, the renal medulla.... isculo
Higad Later, the gluconeogenic mechanisms Corte Medula come into play, which are responsible for renal rena Eritrocitos carrying out the gluconeogenesis carried out by the liver (80%) and the renal Testiculos cortex (20%). Tejidos que sintetizan glucosa
However, after several days of fasting, the renal cortex performs 50% gluconeogenesis, which is carried out
Tejidos que utilizan glucosa comc
1
from various molecules such as glycerol of fatty acids, glucoenergetic amino acids (lactate and alanine). In this way, a very important interaction is established between the liver and the kidney. Gluconeogenesis. Gluconeogenesis is an anabolic pathway that allows
(or GTP). This route has a multiple location, since it begins in the cytoplasm, but it also occurs in the mitochondria and even in the endoplasmic reticulum.
The beginning of the cycle begins with pyruvate, which is found in the cytosol and penetrates the interior of the mitochondria thanks to the hydroxyl, that is, hydroxyl leaves and pyruvate enters.
Once inside the mitochondrion, pyruvate converted to oxaloacetate in a reaction arboxybiotin catalyzed by pyruvate carboxylase that requires biotin. This process requires the presence of CO2 and ATP, leading to an irreversible reaction.
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biotin
Because the mitochondrial membrane does not have an oxaloacetate FOSFOENOL transporter, PIRUVATO before being exported to the cytosol, it must be reduced to malate by mitochondrial COC OXAL CETATO malate dehydrogenase (reversible) at the NADH+H NAD expense of NADH, that is, with energy MALATO expenditure.
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MALATO MALATO NAD Malato-DH NADH OXALACETATO OA 988-8888 DP+P ATP PIRUVATO PIR mitocondri PIRUVATO
The malate leaves the cytosol thanks to a transporter and, once there, it can be oxidized again to oxaloacetate, thanks to a malate dehydrogenase, which an isoenzym