Glycogen digestion

Energy considerations Starch and Glycogen Digestion 01-Amylase (Figure 13.16)... 

C13-0069. Glycogen and cellulose are both polymers of glucose. Explain why humans can use glycogen but not cellulose as an energy source. Why can cows digest cellulose, but humans cannot ... 

Besides his investigations on glycogen, Bernard was concerned with the differences in carbohydrate metabolism between carnivores and herbivores. In the course of these studies he examined the role of the pancreas in digestion and its ability to hydrolyze starch and fats. For his work on the pancreas Bernard was made a Chevalier of the Legion of Honour, the citation stating that the award was for excellent work on the musical [vice medical ] properties of the pancreas (Leicester, 1974). 

This sort of control is usually achieved by either covalent modification (phosphorylation or de phosphorylation as in glycogen metabolism) or by proteolytic cleavage (e.g. activation of digestive enzymes in the gut, or blood clotting mechanism. 

Pupil Salivation Bronchi Heart rate Liver Digestion Adrenal Bladder Genitals Dilation Inhibits Dilates Accelerates Glycogen glucose Inhibits Release of NE, EP Relaxes Stimulates orgasm Constriction Stimulates Constricts Decelerates Glucose glycogen Stimulates (no effect) Constricts Stimulates arousal... 

Activation of the parasympathetic branch causes pupillary dilation, increases salivation, constricts lung bronchi, decelerates heart rate, increases digestion, and stimulates conversion of glycose to glycogen. Whereas the parasympathetic branch is involved in physiological sexual arousal, the sympathetic branch is involved in the physiological aspect of orgasm. 

Also the slowly digesting modified starehes eould be used for the treatment of certain medical conditions (e.g. glycogen storage disease and diabetes mellitus) (Wolf et al., 1999). 

Digestion of the tissue to make glycogen accessible to the anthrone reaction [19,... 

Glycogen and starch ingested in the diet are hydrolyzed by a-amylases, enzymes in saliva and intestinal secretions that break (al—>4) glycosidic bonds between glucose units. Most animals cannot use cellulose as a fuel source, because they lack an enzyme to hydrolyze the (fil—>4) linkages. Termites readily digest cellulose... 

The principal sites of dietary carbohydrate digestion are the mouth and intestinal lumen. Salivary a-amylase acts on dietary starch (glycogen, amylose, amylopectin), producing oligosaccharides. Pancreatic a-amylase continues the process of starch digestion. 

Digestion of dietary glycogen and starch in the human body begins with the salivary and pancreatic amylases, which cleave a-1,4 linkages at random. It continues with a glucoamylase found in the brush border membranes of the small intestine where it occurs as a complex with maltase.74 Carbohydrases are discussed in Chapter 12, Section B. 

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