Glucose synthesis from glycerol

Gluconcogenesis occurs primarily in the liver. It can also occur in the kidney, but this contribution is relatively small. The carbon skeletons used for glucose synthesis can be derived from lactate, glycerol, or amino adds. During exercise, the lactate produced and released by fermentative muscle is taken up by the liver cind... 

B) glycerol, released from adipose tissue, is utilized for glucose synthesis in liver... 

Fig. 33.20. Synthesis of triacylglycerol in liver and adipose tissue. Glycerol 3-phosphate is produced from glucose in both tissues. It is also produced from glycerol in liver, but not in adipose tissue, which lacks glycerol kinase. The steps from glycerol 3-phosphate are the same in the two tissues. FA = fatty acyl group.

Fig. 33.24. Conversion of the fatty acid (FA) from the triacylglycerols (TG) of chylomicrons and VLDL to the TG stored in adipose cells. Note that insulin stimulates both the transport of glucose into adipose cells and the secretion of LPL from the cells. Glucose provides the glycerol 3-phosphate for TG synthesis. Insulin also stimulates the synthesis and secretion of lipoprotein lipase (LPL). Apoprotein C-II activates LPL.

Carbohydrates consumed in excess of caloric need are converted to acetyl CoA, which in turn serves as a source of fatty acids. The concurrent synthesis of glycerol from carbohydrates such as glucose and fructose provides the second precursor needed for the synthesis of triacylglycerols, which are the primary storage form of energy in humans. Excess carbohydrate is converted to fat. 

Gluconeogenic flux from glycerol, synthesis of glycogen, recycling of triacylglycerol, and stimulation of pentose cycle by phenazine metho-sulfate followed. 0 and gave same label distribution in newly synthesized glucose. 

Figure 11.1 Synthesis pathways for propionic acid from glycerol, glucose, and lactate in Propionibacterium.

Tartronic acid, HOOC—CH(OH)—COOH, or hydroxymalonic acid, may be considered as the simplest of the aldaric acids. It has been obtained by the oxidation of glucose or fructose with hydrogen peroxide and ferrous sulfate 40), It is also formed by the cyanohydrin synthesis from glyoxylic acid (41). The oxidation of glycerol gives only small amounts of this acid. 

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