Carbohydrates 2024 PDF

 Generally considered as substances made up of carbon, hydrogen and oxygen.  They are aldehyde or ketone derivatives of polyhydric alcohols and are therefore termed aldoses or ketoses accordingly.  Derived from: hydrate de carbone  Most are found naturally in bound form rather than a...

 Generally considered as substances made up of carbon, hydrogen and oxygen.  They are aldehyde or ketone derivatives of polyhydric alcohols and are therefore termed aldoses or ketoses accordingly.  Derived from: hydrate de carbone  Most are found naturally in bound form rather than as simple sugars ▪ Polysaccharides (starch, cellulose, inulin, gums) ▪ Glycoproteins and proteoglycans ( hormones, antibodies, blood group substances) ▪ Glycolipids (cerebrosides, gangliosides) ▪ Mucopolysaccharides (hyaluronic acid) ▪ Nucleic acids  Green (chlorophyll-containing) plants produce carbohydrates  Dietary intake of plant materials is the major carbohydrate source for humans and animals.  Carbohydrates are defined as aldehyde or keto derivatives of polyhydric alcohols. ▪ Eg. Glycerol on oxidation is converted to D-glyceraldehyde, which is a carbohydrate derived\from the trihydric alcohol (glycerol). 1. Physical appearance: 1. Mono- and disaccharides :white, crystalline 2. Starch- amorphous; cellulose- fibrous 2. Solubility in water 1. Mono- & di- readily soluble in water 2. Starch- slightly soluble 3. Other higher CHO- forms colloidal solutions 4. Cellulose- practically insoluble 3. Sweetness 1. Mono- & di- sweet 2. Starch & cellulose – tasteless  Fructose – 173.3%  Invert sugar - 127-130%  Sucrose - 100%  Glucose - 74.3%  Maltose - 32.5%  Lactose - 16%  Reducing power  Osazone formation- reaction with phenylhydrazine  Reaction with acids: ▪ Disaccharides and polysaccharides will decompose into monosaccharides in the presence of acids. ▪ Pentoses will dehydrate to form furfural, while hexoses will form hydroxymethylfurfural. A. Accdg. To molecular size or to the number of saccharide groups contained in their molecules: 1. Monosaccharides: These are simple sugars containing 1 saccharide group 1a. SUBCLASSIFICATION (Accdg. To # of C atoms) ▪ a.Trioses (C3H6O3)- glyceraldehydes, dihydroxyacetone ▪ b.Tetroses (C4H8O4)- erythrose and erythrulose ▪ c.Pentoses (C5H10O5)- xylose, ribose, deoxyribose, arabinose, rhamnose ▪ d.Hexoses (C6H12O6)- glucose, galactose, mannose, fructose ▪ e.Heptoses (C7H14O7)- mannoheptose, mannoheptulose Monosaccharides C.Accdg. To the number of carbon atoms and the type of carbonyl group present Aldohexose- glucose Ketohexose- fructose A. Accdg. To molecular size or to the number of saccharide groups contained in their molecules: 2.Oligosaccharides: composed of 2-10 disaccharide groups. ▪ -Oligo from Gk word “oligos”-small or few a. Disaccharides (C12H22O11)- sucrose, lactose, maltose, isomaltose b.Trisaccharides (C18H32O18)-raffinose A. Accdg. To molecular size or to the number of saccharide groups contained in their molecules: 3.Polysaccharides (glycans): made up of several saccharide groups. 3.1. Homopolysaccharides (homoglycans): Polymer of same monosaccharide units. ▪ Examples—Starch, glycogen, inulin, cellulose, dextrins, dextrans. 3.2. Heteropolysaccharides (heteroglycans): Polymer of different monosaccharide units or their derivatives. ▪ Example—Mucopolysaccharides (glycosaminoglycans).  Building blocks of all CHO  Either polyhydroxy aldehyde (aldose) or polyhydroxy ketone ketose  Names composed of a stem denoting the number of carbon atoms and the suffix –ose ▪ triose, tetrose, pentose, and hexose signify monosaccharides with, respectively, three, four, five, and six carbon atoms  Six carbon sugars: most abundant in nature  5 carbon sugars: ribose and deoxyribose (RNA, DNA)  4 carbon & 7 carbon: photosynthesis & metabolic pathways  Chiral center is an atom in a molecule that has four different groups tetrahedrally bonded to it.  A chiral molecule is a molecule whose mirror images are not superimposable. Chiral molecules have handedness.  An achiral molecule is a molecule whose mirror images are superimposable. Achiral molecules do not possess handedness.  Stereoisomers are isomers that have the same molecular and structural formulas but differ in the orientation of atoms in space. 2 major structural features that generate stereoisomerism: ▪ (1) the presence of a chiral center in a molecule and ▪ (2) the presence of “structural rigidity” in a molecule. 1. D-GLYCERALDEHYDE 2. DIHYDROXYACETONE  Aldohexose  Normal blood levels: 70-  Most abundant 100mg/dL monosaccharide  Regulated by glucagon &  Aka: dextrose,grape insulin sugar, blood sugar  ↑ blood glucose level= DM  25% less sweet than table sugar  Optical activity: +52o  Primary source of energy of cells  Seldom encountered as monosaccharide  Synthesized from glucose in mammary gland for use in lactose (milk)  Aka: brain sugar  Present in chemical markers used to distinguish blood types  Found in pectin and gums  80 % less sweet than sucrose  Genetic disease- inability of body to metabolize galactose  ↑ galactose in blood and urine  s/s: vomiting, diarrhea, liver enlargement  Can cause death in days  Intervention: remove lactose from diet  http://www.galactosemia.org/galactosemia.html  Ketohexose  Aka: levulose & fruit sugar  Optical activity: -90o  Found in fruit juice and honey  175% sweeter than sucrose  Commercially prepared from inulin  Fructose corn syrup (HFCS)- from milled corn ▪ Being used to replace sucrose in prepared foods and beverages  Aldopentose  Component of: RNA & ATP  It does not occur free in nature but is widely distributed in combination as the polysaccharide mannan, e.g. in ivory nut.  In the body, it is found as a constituent of glycoproteins.  The process whereby a reactant in a chemical reaction loses one or more electrons. (LEORA)  Redox in monosaccharides involve:  All mono- & disaccharides (except sucrose) contains free aldehyde & ketone group (reducing power)  They reduce alkaline metals and are themselves transformed into organic acid Type of Target Product formed Example of sugar acids Oxidizing functional (sugar acids) Agent group Weak o.a. Aldehyde ALDONIC ACID Glucose → GLUCONIC ACID Galactose → GALACTONIC ACID Strong o.a. -Aldehyde ALIDARIC ACID Glucose → GLUCARIC ACID - 1o alcohol Galactose → GALACTARIC ACID Enzymes 1o alcohol URONIC ACID Glucose → GLUCURONIC ACID Galactose → GALACTURONIC ACID  Carbonyl group (aldehyde or ketone) ▪ : reduced to -OH using Hydrogen as reducing agent  D-glucitol: aka. Sorbitol ▪ Uses: moisturizing agents (food & cosmetics); sweetening agent in chewing gum ▪ Also a major factor in formation of cataract due to diabetes  Dulcitol: toxic metabolite seen in patients with galactosemia  Sugar solution when acted upon by microorganisms produces ethyl alcohol and carbon dioxide.  If the process is allowed to continue for some time, ACID is produced  Note: cyclic form of monosaccharides = hemiacetal ▪ HEMIACETAL: An organic compound in which a carbon atom is bonded to both a hydroxyl group (—OH) and an alkoxy group(—OR) Hemiacetal + ROH → acetal GLYCOSIDE: An acetal formed from a cyclic monosaccharide by replacement of hemiacetal carbon –OH with an –OR group  Glucose → glucoside  Galactose → galactoside  -OH of a monosaccharide can react with inorganic oxyacids to form inorganic esters  -OH of a monosaccharide can react with an amino group to produce amino sugar CHITIN HYALURONIC ACID  N-acetyl-β-D-glucosamine  Reducing sugars form characteristic osazone crystals when heated with phenylhydrazine (C6H5NHNH2)  Glucose = Glucosazone = needle-shaped  Fructose= Fructosazone = needle-shaped  Mannose= Mannosazone = needle-shaped  Galactose= Galactosazone = fluffy ball  Lactose= Lactosazone = fluffy ball  Maltose= maltosazone = sunflower shape  Carbohydrate in which two monosaccharide units are bonded together  Formed thru a DEHYDRATION reaction  Bond: glycosidic linkage (C – O - C)  Aka malt sugar  Product of starch hydrolysis  Common in baby foods & malted milk  Monomers: α-D-glucose & D-glucose  Glycosidic Linkage: α(1→4)  Starch Amylodextrin Erythrodextrin Achrodextrin Maltose 2 Glucose units  Intermediate in the hydrolysis of cellulose  Monomers: β-D-glucose & D-glucose  Linkage: β (1→4) Hydrolysis reaction:  Aka: milk sugar  Monomers: β-D-galactose & D-glucose  Linkage: β (1→4)  A genetic condition in which people lack the enzyme lactase thus causes inability of the GIT to hydrolyze lactose  Undigested lactose(intestine) → attract water molecule → s/s: fullness, discomfort, cramping, N/V, diarrhea→ bacterial fermentation (gas)  Aka: table sugar  Monomers: α-D-glucose & β-D-fructose  Linkage: α,β(1→2)  Non-reducing sugar  Optical activity: +66o  Sources: Sugar cane (20%) & Sugar beets (17%)  Sucrose rotation: +66o  Glucose rotation: +52o  Fructose rotation: -92o a) Saccharin b) Cyclamate c) Aspartame (nutra-sweet) d) Sucralose  Contains many monosaccharide units bonded to each other by glycosidic linkage  Aka “glycan” 1. The identity of the monosaccharide repeating unit(s) in the polymer chain  homopolysaccharide is a polysaccharide in which only one type of monosaccharide monomer is present. ▪ Examples: starch, glycogen, cellulose, and chitin  A heteropolysaccharide is a polysaccharide in which more than one (usually two) type of monosaccharide monomer is present. ▪ Examples: hyaluronic acid and heparin, 2. The length of the polymer chain. 3. The type of glycosidic linkage between monomer units. 4. The degree of branching of the polymer chain  is a polysaccharide that is a storage form for monosaccharides and is used as an energy source in cells.  Examples: Starch and glycogen  Storage form of glucose in plants  Monomer: α-D-glucose  Formed by amylose & amylopectin Iodine test: blue-black coloration  Amylose Amylopectin % in starch 15-20% 80-85% Monomer Up to 1000 units Up to 100‚000; branch 25- 30 Glycosidic linkage α (1→4) α (1→4) α (1→6)  Animal starch  Stored in liver and muscle cells  Linkages: α (1→4) , α (1→6)  monomer: up to 1,000,000 units; branch points every 8-12 glucose units  is a polysaccharide that serves as a structural element in plant cell walls and animal exoskeletons.  Examples: cellulose and chitin.  the structural component of plant cell walls,  the most abundant naturally occurring polysaccharide.  Monomer: β-D-glucose ( 5000 units)  Linkage: β (1→4)  Cellulase, an enzyme that can hydrolyze cellulose ▪ Cotton is almost pure cellulose (95%) ▪ Wood is about 50% cellulose.  High fiber food may also play a role in weight control.  MOA: bind lipids such as cholesterol and carry them out of the body with the feces. This lowers blood lipid concentrations and, possibly, the risk of heart and artery disease. ▪ About 25–35 grams daily is a desirable intake  Monomer: N-Acetyl-β -D-glucosamine  Linkage: β (1→4)\  Its function is to give rigidity to the exoskeletons of crabs, lobsters, shrimp, insects, and other arthropods  It also occurs in the cell walls of fungi.  Long, unbranched polysaccharides containing repeating disaccharide unit: ▪ N-acetylgalactosamine or N-acetylglucosamine ▪ Glucoronate or iduronate  Location: surface of cells or extracellular matrix  Uses: ▪ Lubricating fluid in the joints ▪ Structural integrity to cells ▪ Passageway between cells for cell migration  a polysaccharide with a disaccharide repeating unit in which one of the disaccharide components is an amino sugar and one or both disaccharide components has a negative charge due to a sulfate group or a carboxyl group.  Examples: hyaluronic acid and heparin,  N-acetyl-β-D-glucosamine & D-glucuronate  50,000 disaccharide units per chain  Linkages: β(1→3) ; β(1 →4)  Location: Synovial fluid, vitreous humor, ECM of loose connective tissue,  a small polysaccharide with only 15–90 disaccharide residues per chain  D-glucuronate-2-sulfate & N-sulfo-D-glucosamine-6-sulfate  Present in mast cells & is released at the site of injury ▪ Blood anticoagulant  Pharmaceutical anticoagulant ▪ Source: intestinal or lung tissue of pigs & cows 1. Dermatan sulfate ▪ L-iduronate + N-acetyl-D-glucosamine-4-sulfate ▪ Skin, blood vessels & heart valves 2. Chondroitin sulfate ▪ D-glucuronurate + N-acetyl-D-glucosamine-6-sulfate ▪ Cartilage, bone, heart valves 3. Keratan sulfate ▪ D-galactose + N-acetyl-D-glucosamine-6-sulfate ▪ Cornea, bone, cartilage aggregated with choindroitin sufate  Aka MUCOPOLYSACCHARIDES  Linkage of GAGs to the protein: ▪ 2 galactose & a xylulose residue  generally involves the interaction between the carbohydrate marker of one cell and a protein imbedded into the cell membrane of another cell  a protein molecule that has one or more carbohydrate (or carbohydrate derivative) units covalently bonded to it.  Eg: immunoglobulins  is a lipid molecule that has one or more carbohydrate (or carbohydrate derivative) units covalently bonded to it.  eg: cerebrosides, gangliosides,