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MCDB 310 1st Edition Lecture 8Outline of Last Lecture I. Enzyme Kineticsa. Michaelis-Menton Plot and Propertiesb. LIneweaver-Burk plotsII. Enzyme Inhibitiona. Mechanisms of inhibtionIII. Enzyme regulation and modificationsOutline of Current Lecture I. Carbohydratesa. Monosaccharides and namingi. Glycosidic linkagesb. Polysaccharidesi. Homopolysaccharidesii. HeteropolysaccharidesCurrent LectureI. Chapter 7: Carbohydrates - Molecules for structure and energya. Carbohydrate classes: number of subunits, Monosaccharides vs Oligosaccharidesi. Monosaccharides:1. Sugar means “Monomer” - it is the building blockThese 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.2. Sugars tend to be aldehydes and ketones with two ormore hydroxyl groups. The carbons to which these are attached are chiral centers3. D-Glucose (memorize this structure and be able to number the carbons) is the most common sugar4. Names end in -oseii. Oligosaccharides & polysaccharides: short chains of sugarsjoined with glycosidic linkages. Disaccharides are the most common. 1. Oligosaccharides are less than 20 subunits (usually)2. Polysaccharides are more than 20 subunits, but can be up to thousands3. Some chains are linear (line up) and some are branched (don’t line up so nicely)a. differences in bonds cause differences in function4. Starch and cellulose differ greatly in function because of their differences in structurea. Bonds affect structures which affect functionsb. Two Families of Monosaccharidesi. Mostly unbranched carbon chains (open chain or cyclic) with single bondsii. Aldose: carbonyl carbon is at one end (aldehyde)iii.Ketose: carbonyl carbon is anywhere but an end (ketone)iv. See the examples below:v. Can name sugars based on how many carbons are present 1. Example: three carbons —> triosevi.Can also name them based on aldose or ketose1. Example: aldotriose (combination of two naming methods)vii. Usually doesn’t get any morecomplex than 5 or 6 membered ringsin cyclic saccharides1. 4 membered rings have stericproblems2. Some 7/8 membered ringsc. Monosaccharides have asymmetric centersi. causes stereoisomers (remember:2^n, when n is the number ofasymmetrical carbons)ii. Based on the configuration of the chiral center most distant from the carbonyl carboniii.Glyceraldehyde is the standard for which D stereoisomers are identifiedd. Remember: Carbons are numbered started at the carbonyl carbon ende. Epimers: isomers that differ only in rotation about a single carboni. Example: D-glucose and D-mannosef. Some common Monosaccharides are CYCLICi. 5 or more carbons tend to be cyclicii. Carbonyl carbon is bonded to a hydroxyl oxygeniii.Contain an additional asymmetric carbon, so they are stereoisomersiv. Example: D-glucose makes an intramolecular hemiacetal1. Two different molecules are produced based on the configuration at one asymmetrical carbon2. This matters because only one may fit in an active site in an enzyme3. This is the reason D-Glucose is the saccharide predominant in biology —> it fits best into active sites of enzymes4. In comparing the alpha and betaconfigurations:a. Alpha form: oxygen is opposite fromoxygen in hydroxyl groupb. Beta: oxygen is next to the oxygenin the hydroxylc. These matter for making glycosidiclinkages v. Aldohexoses exist as 5-membered and 6-membered rings (depending on how the nucleophilic attackhappens) See the figure to the right1. The names come from what type of organic ring theycome from (ie - pyran and furan)g. Monosaccharides can be reducing agentsi. The end of the sugar that undergoes the oxidation-reduction is called the reducing endii. Only reducing sugars can have a reducing endiii.The reducing end and non-reducing end of the sugar have very different functions (non-reducing end is where more carbons are added)iv. Oxidation of carbons leads to biologically important compounds1. In some sugars hydroxyl is replaced with an amino, alcohol, etc2. Carbonyl carbon can be oxidized to produce an aldonic acid (gluconic acid)3. Carbon farthest from carbonyl can be oxidized to produce a Uronic acid (glucuronic acid)h. Carbohydrates in Diseasei. Sleeping sickness (trypanosomiasis - worms in the blood)1. It is debilitating and often fatal2. It is passed to humans by an insect bite and can pervade nearly all organs3. They are difficult to combat because the antibodies are useless4. The sole source of trypanosoma b. energy is blood glucose5. If you can stop the worms from metabolizing glucose (by adding an enzyme), then the disease will stop spreadingi. Disaccharides: monosaccharidesjoined by o-glycosidic bondsi. Hydroxyl on one sugar plusanomeric carbon of the othersugar ii. The hemiacetal binds withthe alcohol on another toproduce and acetaliii.The new terminus becomesthe new hemiacetal (reducingend)iv. Water is also producedv. Anomers differ only in their rotation about hemiacetal or heiketal carbon1. Hemiacetal or carbonyl carbons are anomeric carbonsvi.Naming:1. Single-headed arrow shows which two carbons are coming together in the condensation reaction2. -syl at end of name: every monosaccharide before the last one in the chain3. -ose at end of name: the final monosaccharide in the chain4. Also need alpha or beta in from of the name5. Notice the curve between the H and O —> going downward it tells us about the 3D structure (has to do with alpha vs beta)a. If alpha: elbow curvesdownb. if beta: elbow curves upvii. Naming exceptions (seefigure):1. non-reducing disaccharidesare called glycosides2. The joined positions areanomeric carbons3. They are represented with aDOUBLE HEADED ARROW(connection betweenanomeric carbons)4. By convention, use thecombination or up/downcurves for glycosidic linkagebetween two anomeric carbonsj. Polysaccharides: glycansi. Have varying degrees of chain length, branching, and types of bondsii. Homopolysaccharides: structural elements and fuels, madeup of all the same monosaccharides1. These are still linked with O-glycosidic linkages2. When branched, have possible different linkagesiii.Heteropolysaccharides: extracellular support in all kingdoms, made up of different monosaccharidesiv. Starch and Glycogen: stored fuels1. If you want to store carbs, you want them to be exceedingly stable (almost chemically inert), so that they can be put to use again2. Polymers of glucose that occur in nature as large aggregate


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