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1、1,Chapter 2. Carbohydrates,Introduction Monosaccharides (单糖) Oligosaccharides (寡糖) Polysaccharides (多糖) Glycoconjugates (复合糖) Analysis of carbohydrates,2,I. Introduction,Existence Functions (功能) Definition (定义) Classification (分类) Characteristic chemical features (化学通性),3,1. Existence,The most abund
2、ant class of organic molecules found in nature Widely distributed in plants and animals Originated from photosynthesis Basic composition: C, H, O (N, P, S) Empirical formula: (CH2O)n Constituting a versatile class of molecules Mono-/oligo-/polysaccharides (单糖/寡糖/多糖) Derivatives (衍生物) Glycoconjugates
3、 (复合糖),I. Introduction,P.1,4,2. Function,Storage of energy (能量贮存) Structural elements (结构成分) Precursors (前体)/intermediates (中间物) of other biomolecules Cell recognition (细胞识别),I. Introduction,P.1,5,3. Definition,葡萄糖,果糖,甘油醛,二羟基丙酮,Carbohydrates are polyhydroxy aldehydes or ketones (多羟基醛/多羟基酮) or substa
4、nces that yield such compounds on hydrolysis.,6,4. Classification,Three major classes of carbohydrates,I. Introduction,7,5. Characteristic chemical features (化学通性),Existence of one or more asymmetric centers (不对称中心) Ability to exist either in linear or ring structures (线状或环状结构) Capacity to form poly
5、meric structures via glycosidic bonds (糖苷键连接) Potential to form multiple hydrogen bonds with water or other molecules (形成氢键的能力),I. Introduction,P.2,8,Two families: aldoses & ketoses (醛糖和酮糖) Stereochemistry (立体化学) Structures: linear & cyclic (线状和环状结构) Properties: physical & chemical (物理和化学性质) *optica
6、l activity and chirality (光活性和手性) Important monosaccharides and their derivatives (重要的单糖及其衍生物),II. Monosaccharides,9,1. Two families: Aldoses & ketoses,Aldoses (醛糖),Ketoses (酮糖),II. Monosaccharides,甘油醛,二羟丙酮,丙糖,己糖,10,Plane-polarized light (平面偏振光 ) Optical activity (旋光性) Chirality (手性) Fischer project
7、ions (Fischer投影式),2. Stereochemistry,II. Monosaccharides,11,(1) Plane-polarized light (平面偏振光 ),Plane-polarized light (平面偏振光) a light with its electric vector vibrating on a specific plane called the plane of polarization (偏振面) Polarimeter (偏振器) an instrument used to measure optical activity.,Polarim
8、eter (偏光计),Light source (non-polarized light) 非偏振光,Polarizer (偏光器),Plane-polarized light (平面偏振光 ),Sample tube,棱 镜,Plane of polarization rotated (偏振面发生了旋转),12,(2) Optical activity (旋光性),A material which can rotate the plane of the plane-polarized light is called to have optical activity, and this mat
9、erial is an optically active substance. (能使平面偏振光的偏振面发生旋转的物质被称为具有旋光性),t = t c l,Rotation (旋光度),Specific rotation (比旋),Concentration (浓度, g/ml),Length (dm),Wavelength (波长, nm),Temperature,Rotation,Clockwise (顺时针) dextrorotatory (右旋光, +),Counterclockwise (反时针) levorotatory (左旋光, ),13,(3) Chirality (手性)
10、,Compounds without chiral centers do not normally show optical acitivity. (没有手性中心的物质没有旋光性) Compounds with one chiral center will show optical activity. (有一个手性中心的物质有旋光性) Compounds with more than one chiral center may or may not show optical activity depending on whether or not they are non-superimpos
11、able on their mirror image (chiral) or superimposable (achiral). (有一个以上手性中心的物质不一定有旋光性),Optically active molecule Chiral molecule (旋光性分子 手性分子),Optical activity (旋光性) Chirality (手性),Chiral centers (手性中心),?,*,*,14,Chiral center（手性中心） Chiral molecule（手性分子） Asymmetric center（不对称中心） n chiral centers 2n ma
12、ximum stereoisomers,True or false: Chiral molecules are always optically active. ( ) Optically active molecules always have chiral centers. ( ) Chiral molecules have always chiral centers. ( ) Molecules with chiral centers are always chiral. ( ),II. Monosaccharides,P.3,n = 4 24 = 16 isomers,15,(4) F
13、ischer projections (Fischer投影式),投影式,甘油醛,(+),(),R,S,D,L,透视式,II. Monosaccharides,P.4,16,Fischer projections,Haworth projections,4 C* 24 = 16 isomers,8 D-forms,8 L-forms,D or L refers to the configuration of the C* farthest from the carbonyl C.,17,Aldoses (醛糖),18,Ketoses (酮糖),II. Monosaccharides,19,Two
14、 systems of specifying the absolute configurations (绝对构型的两种表达体系),Group 4 with the lowest priority,D/L referring to the configuration of the molecule (对整个分子而言) R/S referring to the configuration of a specific C* (对单个C*原子而言),D-glucose 2R,3S,4R,5R-aldohexose (己醛糖),R/S convention priority rules,+/ refer
15、ring to the optical activity of the chiral molecule (指分子的旋光性，与分子或原子的构型无直接关系),20,D-forms of monosaccharides predominate in nature. L-Monosaccharides also exist in nature. D-glucose is the enantiomer of L-glucose. But D-aldohexoses (己醛糖) are not necessarily enantiomers of all of their L-isomers.,II. M
16、onosaccharides,The above four are stereoisomers.,Enantiomer,Enantiomer,Diastereomer,Diastereomer,21,3. Structure,Linear structures (链状结构) Stereoisomers （立体异构体） Enantiomers （对映异构体）: P.4 Diastereomers （非对映异构体）: P.7 Epimers （差向异构体）: P.8 Cyclic structures (环状结构) Anomers （异头物）: P.9,II. Monosaccharides,22,Epimers two sugars that differ only in the configuration around one carbon atom. Epimers are usually diaste
