BCHM 307 1st Edition Lecture 16 Outline of Last Lecture I Chymotrypsin Inhibition A Inhibition through DIFP B Inhibition through TPCK II Coenzymes III Prosthetic Groups Outline of Current Lecture I Carbohydrate Names II Monosaccharides A Fischer Projections B Stereoisomers C D and L Sugars III Cyclic Monosaccharides A Alpha and Beta Anomers IV Disaccharides A Glycosidic Bond B Starch C Glycogen Current Lecture Carbohydrates get their names from being hydrates of carbon Carbohydrates can be broken down into different groups There are monosaccharides which are simple sugars They have a formula that holds true only for them Cn H20 n where n is a number Carbohydrates can be disaccharides like sucrose all the way up to polysaccharides such as starch or cellulose Monosaccharides contain 3 6 carbon atoms These are named respectively as triose tetrose pentose and hexose The monosaccharides contain either aldehyde or ketone functional groups called aldoses or ketoses Combining the names with the functional groups gives the full name of many sugars An example is fructose which is a ketohexose Monosaccharides can be drawn using Fischer projections This is a method using lines to show bonds The carbon that is most oxidized is drawn at the top The carbons are then numbered from top to bottom Horizontal lines indicate extension frontwards Vertical lines indicate the plain extended behind Monosaccharides are chiral and have stereoisomers Within that there are mirror image enantiomers Enzymes are able to distinguish between enantiomers even though they have identical chemical properties These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute The most common enantiomers in nature are D enantiomers Stereoisomers don t have to be mirror images of each other These are known as diastereomers They do not have identical chemical properties and are given different names Whether the sugar is a D or L is determined by the penultimate carbon The penultimate or second to last carbon in the Fischer projection determines this When the hydroxyl group is to the left side of the carbon it is L When the hydroxyl group is on the right side of the carbon it is D In a solution monosaccharides exist as cyclic structures The fifth carbon s hydroxyl group interacts with the first carbon of an aldohexose to form a hemiacetal When the hydroxyl interacts with the second carbon of a ketohexose hemiketals are formed The cyclic sugars are drawn using Haworth projections The extensions on the left side of the Fischer projection drawing will be facing downwards in the cyclic structure The right hand side projects will be facing upwards The reaction that forms these cyclic structures are easily reversible and change constantly The cyclic sugars can be named as alpha anomers if the first carbon s hydroxyl group is facing downwards If it is facing upwards it will be named as a beta anomer Five carbon rings are called furanose structures and six carbon rings are called pyranose structures Disaccharides are formed through a glycosidic bond between monosaccharides The bond is formed through the OH of the anomeric carbon and another OH on the other monosaccharide Water molecules are lost through the bond formation The anomeric carbon loses its ability to switch between alpha and beta anomers when this happens The bonded carbon is named based firstly on the configuration of the anomeric carbon alpha or beta The first number denotes the number of the anomeric carbon The second number is the number of the other carbon involved in this reaction For example maltose is formed through an alpha 1 4 glycosidic bond The three main polysaccharides are starch glycogen and cellulose Starch is also called amylose It has a helical shape to it It contains a nonreducing end and a reducing end that has a free anomeric carbon It is an alpha 1 4 polymer of glucose Starch can be degraded by the enzyme amylase Glycogen is also known as amylopectin It is a highly hydrated molecule that is not tightly packed together It is also an alpha 1 4 polymer of glucose but contains a lot of alpha 1 6 branches Glycogen is used as the storage form of glucose and is found in muscles and the liver
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