Carbohydrate Chemistry Notes PDF

Dr/ MAHMOUD MANSOUR Carbohydrate Chemistry Definition: Carbohydrates are aldehyde (CHO) or ketone (C=O) derivatives of polyhydric alcohols (have more than one OH group). Polyhydroxy-aldehydes or polyhydroxy-ketones. ‫ﻣﻠﻔﺎت ورواﺑط اﻟدورة ﻣﻘﺗﺻرة ﻋﻠﻰ اﻟﻣﺷﺗر...

Dr/ MAHMOUD MANSOUR Carbohydrate Chemistry Definition: Carbohydrates are aldehyde (CHO) or ketone (C=O) derivatives of polyhydric alcohols (have more than one OH group). Polyhydroxy-aldehydes or polyhydroxy-ketones. ‫ﻣﻠﻔﺎت ورواﺑط اﻟدورة ﻣﻘﺗﺻرة ﻋﻠﻰ اﻟﻣﺷﺗرﻛﯾن ﻓﻘط وﻻ ﻧﺣﻠل اﺗﺧداﻣﮭﺎ ﺧﺎرج اﻟدورة‬ Page | 1 Dr/ MAHMOUD MANSOUR  Importance of Carbohydrates: 1- The main Source of energy. 2- Store energy in the form of: starch (in plants) glycogen (in animals and humans) 3- Supply carbon for synthesis of other compounds as proteins 4- Important structural components in animal and plant cells as cell membrane part of nucleic acids and free nucleotides and 5- Important coenzymes. 6- Biological role as a part of hormones and their receptors and enzymes. ‫ﻣﻠﻔﺎت ورواﺑط اﻟدورة ﻣﻘﺗﺻرة ﻋﻠﻰ اﻟﻣﺷﺗرﻛﯾن ﻓﻘط وﻻ ﻧﺣﻠل اﺗﺧداﻣﮭﺎ ﺧﺎرج اﻟدورة‬ Page | 2 Dr/ MAHMOUD MANSOUR  Classification of Carbohydrates: According to number of sugar units in the chain carbohydrates are classified to: Monosaccharides: single sugar unit. (the simplest form of sugars and cannot be further hydrolyzed) Disaccharides: two sugar units, e.g. sucrose. Oligosaccharides: 3 to 10 sugar units.(give monosaccharides on acid hydrolysis) Polysaccharides: more than 10 units.(give monosaccharides on acid hydrolysis) ‫ﻣﻠﻔﺎت ورواﺑط اﻟدورة ﻣﻘﺗﺻرة ﻋﻠﻰ اﻟﻣﺷﺗرﻛﯾن ﻓﻘط وﻻ ﻧﺣﻠل اﺗﺧداﻣﮭﺎ ﺧﺎرج اﻟدورة‬ Page | 3 Dr/ MAHMOUD MANSOUR Monosaccharides ֎ Definition: Monosaccharaides are the building units of carbohydrates, They are the simplest sugars that cannot be hydrolyzed. The general formula of monosaccharides is (C n H 2 n O n). ֎ Classification of Monosaccharides: (I) According to the presence of Aldhyde or ketone group: (Active group) (a) Aldoses: contain aldhyde group (eg: glyceraldehyde) (b) Ketoses: contain ketone group (eg:Dihydroxy acetone) a Ketone can be indicated with the suffix (ulose) ‫ﻣﻠﻔﺎت ورواﺑط اﻟدورة ﻣﻘﺗﺻرة ﻋﻠﻰ اﻟﻣﺷﺗرﻛﯾن ﻓﻘط وﻻ ﻧﺣﻠل اﺗﺧداﻣﮭﺎ ﺧﺎرج اﻟدورة‬ Page | 4 Dr/ MAHMOUD MANSOUR According to the number of carbon atoms::  Triose: contain 3 carbon atoms.  Tetrose: contain 4 carbon atoms.  Pentose: contain 5 carbon atoms.  Hexose: contain 6 carbon atoms.  Heptose: contain 7 carbon atoms. According to the number of carbon atoms & active group: Number of Aldose Ketose Carbons Triose Glyceraldehyde. Dihydroxyacetone. Tetrose Erytherose. Erythrulose. Pentose Ribose,Xylose. Ribulose, Xylulose. Glucose Fructose. Hexose Galactose Mannose The suffix -ose is used in biochemistry to form the names of sugars. ‫ﻣﻠﻔﺎت ورواﺑط اﻟدورة ﻣﻘﺗﺻرة ﻋﻠﻰ اﻟﻣﺷﺗرﻛﯾن ﻓﻘط وﻻ ﻧﺣﻠل اﺗﺧداﻣﮭﺎ ﺧﺎرج اﻟدورة‬ Page | 5 Dr/ MAHMOUD MANSOUR Page | 6 Dr/ MAHMOUD MANSOUR  Asymmetric carbon atom: The carbon atom attached to which 4 different groups or atoms.  Importance of asymmetric carbon atom 1- It makes the compound optically active. 2. Isomerism. OPTICAL ACTIVITY Definition: It is the ability of the sugar to rotate the plane of the plane polarized light. The sugar that rotates the light to the right is called dextrorotatory (d or +) such as glucose, galactose and starch And that rotating light to the left is called levorotatory (l or -) such as fructose. Ordinary light vibrates in all directions. Ordinary light can be changed to plane polarized light by passing it through a prism made of calcium carbonate. Plane polarized light vibrates in one plane and direction. ‫ﻣﻠﻔﺎت ورواﺑط اﻟدورة ﻣﻘﺗﺻرة ﻋﻠﻰ اﻟﻣﺷﺗرﻛﯾن ﻓﻘط وﻻ ﻧﺣﻠل اﺗﺧداﻣﮭﺎ ﺧﺎرج اﻟدورة‬ Page | 7 Dr/ MAHMOUD MANSOUR Cyclization of monosaccharides Haworth's projection formula:  Less than 1% of each of the monosaccharides exists in the open-chain form.  They are predominantly found in a ring (cyclic) form.  Types of cyclic forms (Rings): Pyranose Furanose (pyran ring) (Furan ring) Refers to a six-membered ring Denotes a five-membered ring consisting of five carbons and one with four carbons and one oxygen oxygen ‫ﻣﻠﻔﺎت ورواﺑط اﻟدورة ﻣﻘﺗﺻرة ﻋﻠﻰ اﻟﻣﺷﺗرﻛﯾن ﻓﻘط وﻻ ﻧﺣﻠل اﺗﺧداﻣﮭﺎ ﺧﺎرج اﻟدورة‬ Page | 8 Dr/ MAHMOUD MANSOUR Isomerism  Isomers: they are molecules having the same chemical formula but differ in distribution of their atoms.  Types of isomers : 1) Functional group Isomerism 2) Enatiomars (D & L isomerism). 3) Anomers (ɑ & β isomerism). 4) Epimers 1) Functional group isomerism: They are isomers that have the same carbon skeleton. But have different functional groups (aldehyde or ketone). eg: Glyceraldehyde & Dihydroxyacetone. ‫ﻣﻠﻔﺎت ورواﺑط اﻟدورة ﻣﻘﺗﺻرة ﻋﻠﻰ اﻟﻣﺷﺗرﻛﯾن ﻓﻘط وﻻ ﻧﺣﻠل اﺗﺧداﻣﮭﺎ ﺧﺎرج اﻟدورة‬ Page | 9 Dr/ MAHMOUD MANSOUR 2)Enantiomers (D & L isomerism):‫ھﻢ ﻧﻔﺲ اﻟﺴﻜﺮ‬  They are steroisomers which differ in the distribution of (H) & (OH) group around the subterminal asymmetric carbon atom.  If (OH) group to the right of sub terminal atom → (D- form) eg: D-glyceraldehyde.  If (OH) group to the left of sub terminal atom → (L- form) eg: L-glyceraldehyde.  This difference make the two forms mirror image to each others.  They are called Enatiomars. ♠ Almost all naturally occurring Carbohydrates are of D-configuration. ‫ﻣﻠﻔﺎت ورواﺑط اﻟدورة ﻣﻘﺗﺻرة ﻋﻠﻰ اﻟﻣﺷﺗرﻛﯾن ﻓﻘط وﻻ ﻧﺣﻠل اﺗﺧداﻣﮭﺎ ﺧﺎرج اﻟدورة‬ Page | 10 ‫‪Dr/ MAHMOUD MANSOUR‬‬ ‫ﻣﻠﻔﺎت ورواﺑط اﻟدورة ﻣﻘﺗﺻرة ﻋﻠﻰ اﻟﻣﺷﺗرﻛﯾن ﻓﻘط وﻻ ﻧﺣﻠل اﺗﺧداﻣﮭﺎ ﺧﺎرج اﻟدورة‬ ‫‪Page | 11‬‬ Dr/ MAHMOUD MANSOUR 3) Anomers (ɑ & β isomerism): ‫ﺑﺮﺿﻮ ﻧﻔﺲ اﻟﻤﺮﻛﺐ ﺑﺲ ھﻨﺎ ﺣﻠﻘﻲ‬  They are steroisomers which differ in the distribution of (H) & (OH) group around the asymmetric anomeric carbon atom.  Anomeric carbon atom:C1 in aldoses & C2 in ketoses are symmetric carbon atom, but after ring formation they become asymmetric.  If (OH) group at anomeric carbon is on: the right side (below the plane) this is called ɑ-form. the left side (above the plane ) it is called β form. eg: ɑ-Glucose & β-Glucose. Page | 12 Dr/ MAHMOUD MANSOUR 4) Epimers:  They are steroisomers which differ in the distribution of (H) & (OH) group around Single asymmetric carbon atom other than the anomeric carbon (C1 in aldoses or C2 in ketoses) and the subterminal carbon (D&L)  Glucose is an epimer to each of mannose & galactose.  Mannose and galactose are not epimer to each others. ֎ galactose C4 OH at left side and Glucose C4 OH at right side. ֎ Mannose C2 OH at left side and Glucose C2 OH at right side. ‫ﻣﻠﻔﺎت ورواﺑط اﻟدورة ﻣﻘﺗﺻرة ﻋﻠﻰ اﻟﻣﺷﺗرﻛﯾن ﻓﻘط وﻻ ﻧﺣﻠل اﺗﺧداﻣﮭﺎ ﺧﺎرج اﻟدورة‬ Page | 13