February 1, 2010 Biochemistry Polysaccharides: In terms of structural starch, and linear 1(4 Linkages that constitute Amylose and amylopectin (1 ( 6). In the form of storage starch in humans, is called Glycogen. Glycogen is similar to plant amylopectin. This is called a limit dextrin (hydrolysis limit) without the additional presence of an alpha 1(6 cleavage enzyme. With branching, it allows you to compact more into a cell. Cellulose: the most abundant carbohydrate in the biosphere. It resists hydroliphic cleavage. Hemicellulose: xylose and arabinose are the two next predominant sugars that typically exist in beta 1(4 linkages. These are structural carbs in plants secondary cell walls. A favorite question of mine for Carbs: I will ask you to draw/sketch any aldohexose, aldopentose, ketohexose, ketopentose. Don?t name it. But you need to know what a generic structure looks like. Tell me, is it a D or L? Or I might ask you to draw it as a D or as an L. Then I might ask you, if it is allowable, draw the furanose (5 sides) form or pyranose (6 sides) form. Now I might ask you to take another sugar that you have been asked to draw and form a furanose or a pyranose. Now take what you?ve drawn and connect them Beta 1(3, etc. I might give you the parent compound. So take what I have given you and draw whatever you are asked. He will give the structures for everything that we need to draw something. I might give you a picture of glucose and ask you to draw the pyranose structure of the glucose, show the anomeric carbon in the beta position, and now form a N-glycosil linkage at position 2. Now I?ll say connect it with a molecule of some kind of acid given in a fischer projection that you will need to put into pyranose form. Then I will ask to connect them beta 1(3. But I would give you the structures for everything. Biochemical implications of ?C=C- When you encounter a C=C it is, for the most part, Cis. Cis is more predominant in nature. Multiple C=C are not conjugated (-CH=CH-CH=CH-). What we see is divinylmethane repeat pattern. In higher animals, we do see these conjugated atoms: beef cattle, sheep, deep. Animals that contain fiber digesting bacteria in their Rumen. They will secrete conjugated fatty acids into their milk.
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