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Flashcards in Carbohydrate Structure & Function Deck (19):
1

Classification Strategies for Carbs

1. Nomenclature
2. StereoChemistry

2

Nomenclature

pg. 109 (Memorize Structures)

1. Triose, Tetrose, Pentose, Hexose [Carbs w/ 3,4,5,6 C]
2. Aldehydes vs. Ketones

3

Stereochemistry Terminology

Stereoisomers/Optical isomers
1. Enantiomers--non-super-imposable, mirror images
2. Diasteriomers--non-super-imposable, non-mirror
images
3. Epimers--diasteriomers with opposition at only 1 c

Properties of Stereoisomers
1. Absolute Configuration [R&S or D&L]
2. Optical Rotation [+ or -]---determined experimentally

Stereoisomer Depiction Method:
1. Fischer Projection [HA lines-wedges-out of the page;
VA lines-dashes-into the page]

4

Optical/Stereoisomers

Carbohydrates that possess identical formulas but differ in spatial arrangement of their groups

5

Absolute Configuration

Stereoisomer property that determines spatial arrangement of molecules around CCs

6

Cyclic Sugars Terminology

Types of cyclic sugars:
1. Hemiacetals --- Aldehyde sugars
2. Hemiketals ---- Ketal sugars

Most Stable Cyclic Sugars:
1. Pyranose---6 C
2. Furanose --5 C

Stereoisomer Depiction Method:
1. Haworths Projection
2. Chair Configuration--either Alpha or Beta anomers

Types of Stereoisomers:
1. Alpha Anomer--Trans/axial anomeric OH to -
CH2OH
2. Beta Anomer --Cis/equatorial anomeric OH to -
CH2OH

7

Mutarotation

Rapid Transition of cyclic sugars b/w the alpha and beta anomeric configurations in solution

***[Beta Configuration] > [Alpha Configuration] in a solution at equilibrium b/c it exerts lesssteric hindeerance due to its equatorial anomeric OH position

8

Rxns Monosaccharides Undergo

1. Oxidation-Reduction
2. Nucleophilic-Attack/Glycoside-Formation
3. Esterification

9

Oxidation Reduction Rxns of Monosaccharides Terminology

Oxidation Nomenclature of open-chain sugars
1. Aldoses--->Aldonic Acids
2. Ketoses--->Ketonic Acids

Oxidation Nomenclature of cyclic sugars
1. Hemiacetals & hemiketals--->Lactones

Oxidizing Agents Used for Detecting Reducing Sugars in a Solution:
1. Tollen's Reagent---Uses Ag((NH3)2)+---Ag+
becomes metallic silver in
presence of reducing sugars
2. Benedict's Reagent---Cu2O precipitate forms in
presence of reducing sugars

****Before being oxidized to carboxylic acids, ketones first undergo tautomerization to form an aldose/enol****

Reduction Nomenclature of sugars
1. Aldose--->Alditol
2. Ketose--->Ketol

10

Deoxy-Sugar

Sugar that replaces a aldetol's OH group with H alone
Ex: Sugar group of DNA

11

Esterification of Saccharides

Rxn Elements:
1. COOH + Monosaccharides ---> ROR/esters

****Rxn of OH groups of Monosaccharides and carboxylic acids/CA derivatives to form esters [....O...]****

Ex:
1. Phosphorylation of glucose catalyzed by hexokinase or glucokinase in the liver

12

Glycosidic Rxns of Monosaccharides

Rxn Elements
-H2O
1. ROH + Hemiacetals---> alpha or beta
Acetals [aka Glycosides]

Rxn Type: Dehydration Rxn

Potential Types of Glycosides:
1. Pyranosides
2. Furanosides

Type of Bond Formed
1. Glycosidic Bond [alpha or beta anomeric #, #]

***Allow formation of di/polysaccharides****

13

Complex Carbohydrates

Carbohydrates with 2+ sugar moieties

Complex Carbohydrates created by Glycosidic Bonds:
1. Disaccharides
2. Oligosaccharides
3. Polysaccharides

14

Glycosidic Bonds in Complex Carbohydrates

Notation:
[Type of sugar-alpha or beta anomeric-#, #-type of
sugar]

***In formation of glycosidic bonds, an alpha or beta anomeric OH of one sugar moiety forms a bond with any OH group of the other sugar moiety****

Ex: [glucose-alpha-1, 6-fructose] meaning the alpha anomeric OH of one sugar moiety bonded to the OH on C-6 of the second sugar moiety!

15

Important Disaccharides Produced in the Body

1. Maltose
2. Lactose
3. Sucrose

***pg 120***

16

Polysaccharides

Types of Polysaccharides
1. Homo vs. Heteropolysaccharides
2. Linear Vs. Branched---[Constituent monosaccharide
contains 2+ glycosidic bonds]

Biologically Important Polysaccharides:
1. Cellulose ]
2. Glycogen ] ****All are composed of D-glucose
3. Starch ]

17

Cellulose

1. Homopolysaccharide chain of B-1,4-D-glucose held together by H-bonds
2. Main constituent of plants that serves as a source of fibers in humans given that it can't be digested due to lack of cellulase enzyme

18

Starch

Chemical Structure
1. Homopolysaccharide with a-1,4-D-glucose links
2. Types:
A. Amylose---
I. linear with a-1,4-D-glucose links
II. degraded with a- or b- amylase
B. Amylopectin---
I. branched with a-1,6-D-glucose links
II. degraded with branching enzymes

Real-life Implication
1. Main energy reservoir in plants
2. Digestable in humans


***Presence of starch in a solution can be tested with an Iodine Reagent***

19

Glycogen

Chemical Structure
1. Chemical Nature
I. highly branched homopolysaccharide with a-
1,4-D-glucose & a-1,6-D-glucose glycosidic links
*****similar to but more branched than
amylopectin****
2. Digestion
I. cleaved by Glycogen Phosphorylase at the non-
reducing end of branches

Real-Life Implication
1. Primary reservoir of energy in animals