. Biochemistry of plants and animals, an introduction. Biochemistry. 68 GENERAL BIOCHEMISTRY lose may be represented by a long chain of glucose rings connected as shown for its associated carbohydrate. The hexagons represent the usual configurations of the first five carbons of the a-o-glucose sub- units. Glycogen Animal starch is the principal reserve carbohydrate of animals and is most abundant in muscle and liver. The same or a very similar carbohydrate occurs in yeast and certain fungi. Glycogen resembles amylopectin rather closely in both physical and chemical properties but is not identi
. Biochemistry of plants and animals, an introduction. Biochemistry. 68 GENERAL BIOCHEMISTRY lose may be represented by a long chain of glucose rings connected as shown for its associated carbohydrate. The hexagons represent the usual configurations of the first five carbons of the a-o-glucose sub- units. Glycogen Animal starch is the principal reserve carbohydrate of animals and is most abundant in muscle and liver. The same or a very similar carbohydrate occurs in yeast and certain fungi. Glycogen resembles amylopectin rather closely in both physical and chemical properties but is not identical with it. Similar linkages involving a-D-glucose occur in both carbohydrates, although the number and length of the branches may ditfer somewhat. The schematic structure of glycogen would be like that of amylopectin shown above. Cellulose This polysaccharide is also based on glucose, and the linkages are 1-4. However, the glucose is in the /3 form as chains of glucose units. Thus the structure of cellulose might be indicated by CH2OH. representing a chain of great length. Ihese rather linear arrange- ments are packed together to form the fibers of cotton and to serve as the structural materials in plants. Besides carbon dioxide (free and in solution), mineral carbonates, coal, and perhaps petroleimi, cellulose is probably the most abundant organic material. In fact, it is estimated that the quantity of carbon dioxide fixed as cellulose is about half the weight of this gas in the atmosphere. From this relationship it is clear that cellulose must be steadily degraded by bacteria and fungi, and the carbon dioxide re- turned to the atmosphere in order to maintain the carbon cycle. Celhdose is resistant to the amylases attacking starch. The presence of the /3 form of glucose introduces a different enzyme specificity, and animals ordinarily do not possess enzymes capable of breaking cel- lulose into soluble fragments. However, the bacterial flora of certain animals do hydrolyze pa
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