12 Glycolysis - B iochemis ry E duca ion Department of...

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Unformatted text preview: B iochemis ry E duca ion Department of iochemistry & Molecular iology University of New Mexico BIOC 423 Int oducto y Biochemist y Carbohydrates; Glycolysis OBJECTIVES Sugars Understand the difference between the structures of aldoses and ketoses, hemiacetals and hemiketals Be able to draw the structures of glucose and fructose. Know the structures of the disaccharides sucrose and lactose and understand the differences between and glycosidic linkages. Glycolysis Understand the overall purpose of glycolysis. Know: o the NAMES, STRUCTURES, ENZYMES, COFACTORS of all of the steps of glycolysis o The TYPE of reaction catalyzed by each enzyme o the NET EQUATION of glycolysis OUTLINE Structure of Simple Sugars Definitions of sugars reviewed Inter-conversion of monosaccharides Glucose Introduction to Metabolism Glycolysis - Central Pathway of Metabolism Why you need to know names, structures, enzymes, cofactors and regulation LECTURE In all species carbohydrates provide the central or common core of metabolism. In multicell organisms the simple sugar glucose is the common fuel molecule that can be utilized by all cells. Just like ATP, glucose can be thought of as a common energy currency. The difference is that ATP is limited to intracellular locations whereas glucose can be thought of as moving potential ATP from one cell to another. Review of Carbohydrates We have already discussed carbohydrates and this section is meant to simply reinforce some definitions. Carbohydrates = polyhydroxy aldehydes and ketones Monosaccharides simplest carbohydrates: aldehydes or ketones with hydroxylated methylene groups - empirical formula (CH 2 O) n n = 3, triose n = 4, tetrose n = 5, pentose n = 6, hexose aldose - aldehyde sugar ketose - ketone sugar The two smallest monosaccharides are the trioses: glyceraldehyde and dihydroxyacetone Glyderaldehyde is an aldose with one asymmetric carbon. The only isomer we will be dealing with is the D isomer. Dihydroxyacetone is a symmetrical molecule and a ketose. If we extend the above series by adding CH-OH units, a tetrose (C 4 ) has 2, a pentose (C 5 ) 3, and a hexose (C 6 ) 4 additional asymmetric carbons. For monosaccharides with more than 1 asymmetric carbon, the absolute configuration, given as a prefix to the name of the compound, refers to the asymmetric carbon that is farthest from the carbonyl and defines the isomer (D or L). Stereochemistry around each of the additional carbons, define new molecules which are called epimers . If n = number of assymmetric carbons, the number of stereoisomers is 2 n . Clearly, there are lots of different carbohydrates and lots of names. enantiomers- mirror image steroisomers epimers- steroisomers that differ in configuration about only 1 asymmetric carbon atom diastereomers- stereoisomers that are not enantiomers Glucose, fructose, most common Do not try to memorize all of them, for this course focus on Glucose and Fructose only....
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12 Glycolysis - B iochemis ry E duca ion Department of...

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