Description
1. Contact me at kgahern@davincipress.com / Friend me on Facebook (kevin.g.ahern)
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Highlights Carbohydrates 2
1. Disaccharides are carbohydrates with two monosaccharide subunits. The most common disaccharide is sucrose, which contains a subunit of glucose linked to a subunit of fructose via glycosidic bonds between each. Note that the anomeric bond of glucose is alpha, whereas the anomeric bond of fructose is beta.
2. Another common disaccharide is lactose (glucose + galactose, linked in an alpha-1,4 bond). Lactose is abundant in milk. Maltose is a disaccharide of glucose
3. Attachment of an amino group to carbon #2 is a common modification of sugars. The amine group can come from a protein side chain, making a glycoprotein (molecule with sugar and protein). Glycoproteins are used in cellular identity (blood typing, for instance).
4. Cellulose is a polysaccharide composed solely of glucose subunits. The glucose subunits all have beta-1,4 bonds. Humans and most non-ruminant animals cannot digest cellulose to obtain glucose because they do not have enzymes that will attach the beta-1,4 bonds. Ruminants contain a bacterium in their rumen with an enzyme called cellulase that will break beta-1,4 bonds and release free glucose. Cellulose is a component of plant cell walls and gives them structural integrity.
5. An energy storage polymer of glucose in plants is starch, which contains amylose (a straight chain polymer of glucose with only alpha-1,4 bonds) and amylopectin (a branched chain polymer of glucose with both alpha-1,4 and alpha-1,6 bonds). Both amylose and amylopectin can readily be digested by animals.
6. Branching of amylopectin (and of glycogen - the equivalent in animals) is important because animals digest carbohydrates starting at the ends. The more ends available (such as when there is branching), the more glucose that can be quickly released.
7. Chitin is a polysaccharide of insects that is composed of repeating subunits of an amino sugar (N-acetyl-glucosamine).
8. Proteoglycans are molecules that link long carbohydrate polymerse to proteins. The polymers usually contain sugars that have negative groups attached to them, which alter their chemistry and cause them to be "slimey." Mucus and synovial fluid contain proteoglycans.
9. Glycoproteins can stimulate an antigenic (immune) response. Glycoproteins are the form of the carbohydrates described in class previously that give identity to cells. Such glycoproteins are responsible for organ rejection and, in the case of blood cells, blood typing.
Highlights Glycolysis
1. Glycolysis is a metabolic pathway for the breakdown (catabolism) of glucose and related sugars. The pathway requires two ATPs to start the process and generates 4 ATPS (for a net of two ATPs) per glucose. Also generated during glycolysis are two NADHs.
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