同济大学：《细胞的生物化学》课程电子教案（课件讲稿）碳水化合物与碳水化合物代谢 Carbohydrates and Carbohydrate metabolism

Carbohydrates and Carbohydrate metabolism

Carbohydrates and Carbohydrate metabolism

It is hardly surprising that much of the early biochemical research was concerned with the study of proteins.Proteins form the class of biological macromolecules that have the most well-defined physico- chemical properties and consequently are generally easier to isolate and characterize than nucleic acids,polysaccharides,or lipids. Furthermore,proteins,particularly in the forms of enzymes,have an obvious biochemical function.The central role that proteins play in biological processes has therefore been recognized since the earliest days of biochemistry.In contrast,the task of nucleic acids in the transmission and expression of genetic information was not realized until the late 1940s,the role of lipids in biological membranes was not appreciated until the 1960s,and the biological functions of polysaccharides are still somewhat mysterious. (Donald Judith Voet,1990)

Carbohydrate metabolism

1.Complex carbohydrates are heterogenious and not easy to characterize by physical and/or chemical analysis. 2.Carbohydrates are not genetically determined.Complex structure are build by a sequential addition of monomeres using different enzymes. 3.Carbohydrates have usually passive functions within cells.Thus functional assays to measure its biological activity are difficult to develop. Nevertheless:carbohydrates are essential compounds in all cells 1.Energy metabolism and energy storage. 2.Ribose and deoxyribose as components of RNA DNA. 3.Carbohydrates are essential components of glycoproteins and glycolipids. 4.Carbohydrates are important components of zell walls of bacteria and plants

1. Complex carbohydrates are heterogenious and not easy to characterize by physical and/or chemical analysis. 2. Carbohydrates are not genetically determined. Complex structure are build by a sequential addition of monomeres using different enzymes. 3. Carbohydrates have usually passive functions within cells. Thus functional assays to measure its biological activity are difficult to develop. Nevertheless: carbohydrates are essential compounds in all cells ! 1. Energy metabolism and energy storage. 2. Ribose and deoxyribose as components of RNA / DNA. 3. Carbohydrates are essential components of glycoproteins and glycolipids. 4. Carbohydrates are important components of zell walls of bacteria and plants

Important terms of Carbohydrate Chemistry ●Aldoses Ketoses ●Trioses,Tetroses, Chair and Boat Configurations Pentoses,Hexoses, Furanoses Pyranoses Heptoses Hemiacetals Hemiketals Haworth-/Fischer-Projection Isomeric ●Mutarotation ●Epimeric Forms ●Sugar alcohols Anomeric ●Sugar acids Deoxy sugars,Amino sugars

Aldoses I Ketoses Chair and Boat Configurations Furanoses I Pyranoses Hemiacetals I Hemiketals Haworth- I Fischer-Projection Mutarotation Sugar alcohols Sugar acids Deoxy sugars, Amino sugars Important terms of Carbohydrate Chemistry Isomeric Epimeric Forms Anomeric Trioses, Tetroses, Pentoses, Hexoses, Heptoses

Isomeric structures Isomeric(greak ioouapng):isos equal;meros part Compounds of identical molecular formula but different structures I constitutional isomers structural isomers like ethanol and dimethylether CH3-CH,-OH CHz-O-CH3 ll stereomeric isomers 1.Configurational isomers In stereoisomers the bond structure is the same,but the geometrical positioning of atoms and functional groups with respect to optically active C atoms differs. This class includes enantiomers where different isomers are non-superimposable mirror-images of each other,and diastereomers when they are not.This also in- cludes cis-trans isomers or geometric isomers,respectively

Isomeric structures Isomeric (greak ἰσομερής): isos = equal; meros = part Compounds of identical molecular formula but different structures I = constitutional isomers structural isomers like ethanol and dimethylether CH3 -CH2 -OH CH3 -O-CH3 II = stereomeric isomers 1. Configurational isomers In stereoisomers the bond structure is the same, but the geometrical positioning of atoms and functional groups with respect to optically active C atoms differs. This class includes enantiomers where different isomers are non-superimposable mirror-images of each other, and diastereomers when they are not. This also in￾cludes cis - trans isomers or geometric isomers, respectively

1.Conformational isomers These conformers can be superimposed by a simple roation along one ore more single bonds within the molecule.It should be noted,however,that conformers have usually different physico-chemical stabilities because of disturbances between two or several groups in space.A good example in this respect is butan. CH3 CH3 CH3 CH3 CH3 Anomeric forms,i.e.the axial or equatorial orientation of atoms or groups in ring systems(a-or B-glucose for example)does also belong to the group of conform- ational isomers

1. Conformational isomers These conformers can be superimposed by a simple roation along one ore more single bonds within the molecule. It should be noted, however, that conformers have usually different physico-chemical stabilities because of disturbances between two or several groups in space. A good example in this respect is butan. CH3 H H CH3 H H CH3 H H H H CH3 Anomeric forms, i.e. the axial or equatorial orientation of atoms or groups in ring systems (a- or b- glucose for example) does also belong to the group of conform￾ational isomers. CH3 CH2 CH2 CH3

Aldoses Ketoses Aldoses and ketoses are tautomeric forms,i.e.they are isomeric compounds differing only in the positon of a proton and the concomittant exchange of a chemical bond. c=0 H H H一 一OH H一C一OH C=0 H一C一OH H一C一OH H一C一OH H一C一OH H,C-OH H2C-OH D-Ribose D-Ribulose

Aldoses - Ketoses Aldoses and ketoses are tautomeric forms, i.e. they are isomeric compounds differing only in the positon of a proton and the concomittant exchange of a chemical bond. C C C C C O OH OH OH OH H H H H H2 C C C C C OH O OH OH OH H H H H H2 D - Ribose D - Ribulose

Mirror image Chirality

Chirality Mirror image

Chirality (Chemistry) In chemistry chirality (artificial word from the greak word xalp=hand)means the stereometric organization of atoms in a way that it cannot be superimposed to its mirror image.A chiral object and its mirror image are called enantiomers.Both enantiomers of a chiral molecule find its analogy in the left and the right hand. In organic chemistry,the easiest form of chirality is found if a C atom within a molecule has 4 different substituents.This C atom is called a stereo center, a chirality center or an asymmetric C atom

Chirality (Chemistry) In chemistry chirality (artificial word from the greak word χειρ = hand) means the stereometric organization of atoms in a way that it cannot be superimposed to its mirror image. A chiral object and its mirror image are called enantiomers. Both enantiomers of a chiral molecule find its analogy in the left and the right hand. In organic chemistry, the easiest form of chirality is found if a C atom within a molecule has 4 different substituents. This C atom is called a stereo center, a chirality center or an asymmetric C atom

light source Chiral molecules changing the angle of polarized light polarizer sample tube analyzer viewer

Chiral molecules changing the angle of polarized light