CarbohydratesVersion 1.111Carbohydrates Contain Carbon, Hydrogen and Oxygen Can be characterized as Monosaccharides Disaccharides Polysaccharides Includes sugars, starches, cellulose,2Carbohydrates Carbohydrates are produced in green plants in the presence of chlorophyll and sunlight in a process known as photosynthesis. They serve as food sources for living organisms and provide the structural support for plants. Many carbohydrates are large polymers composed of repeating units of simple sugars.3Types of Carbohydrates Monosaccharides - simple sugars with multiple -OH groups. Based on number of carbons (3, 4, 5, 6), a monosaccharide is a triose, tetrose, pentose or hexose. Disaccharides - Two monosaccharides linked by a covalent bond. Oligosaccharides - a few monosaccharides linked by covalent bonds Polysaccharides - polymers consisting of chains of multiple monosaccharide or disaccharide units. I ( H2O)nr H - -HIarbohydrates have the f ll wing basic c mp siti n:4fructoseMonosaccharides Single (simple) sugars Contain C, H, and O in a 1: :1 ratio Quick energy sourcesExamples: Examples:GlucoseC6H1 O6Fructose C6H1 O6Galactose C6H1 O6glucoseCarbohydrates5GlucoseFructoseMonosaccharides Empirical formula is CH O Both open chain and ring structures are possible Mulitple structural isomers are possible Multiple chiral carbon atoms lead to optical isomers Monosaccharides generally have between 3 and 6 carbon atoms The most common monosaccharides are: Five carbons C5H10O5 - called pentosesSix carbonsC6H1O6- calledhexoses Monosaccharide straight chains have at least one carbonyl group C=O. If the carbonyl group is at the end it is an aldosesugar.If it is within the chain it is a ketose sugar6MonosaccharidesAldoses (e.g., glucose) have an aldehyde group at one end.Ketoses (e.g., fructose) have a ketone group, usually at C . CC OH HC H HOC OH HC OH HCH2OHD-glucoseO H C H HOC OH HC OH HCH2OHCH2OHC OD-fructose7Optical Isomers:D and L FormsD or dextrorotatory&L orlevorotatory are designationsfor optical isomers that are based on the configuration about the single asymmetric C in glyceraldehyde.The lower representations are Fischer Projections.CHOCCH2OHHO HCHOCCH2OHH OHCHOCCH2OHHO HCHOCCH2OHH OHL-glyceraldehyde D-glyceraldehydeL-glyceraldehydeD-glyceraldehyde8Sugar NomenclatureFor sugars with more than one chiral center,D and L referto the asymmetric C farthest from the aldehyde or keto group. Most naturally occurring sugars are D isomers.O HO HCC H C OHHO C HHO C HH C OH H C OHHO C H H C OHHO C HCH2OH CH2OHD-glucose L-glucose9D & L sugars are mirror images of one another. They have the same name, e.g., D-glucose & L-glucose. Other stereoisomers have unique names, e.g., glucose, mannose, galactose, etc. The number of stereoisomers is n, where n is the number of asymmetric centers. The 6-C aldoses have 4 asymmetric centers. Thus there are 16 possible stereoisomers (8 D-sugars and 8 L-sugars).O HO HCC H C OHHO C HHO C HH C OH H C OHHO C H H C OHHO C HCH2OH CH2OHD-glucoseL-glucoseSteroisomers10Ring StructuresPentoses and hexoses can form ring structures as the ketone or aldehyde reacts with a distal OH.Glucose forms an intra-molecular hemiacetal, as the C1 aldehyde& C5 OH react, to form a 6-member ring known as a pyranose ring, These representations of the cyclic sugars are called Haworth projections. HOOHHOH HOHCH2OHHOHH HOOHHOH HOHCH2OHHHOHE-D-glucose F-D-glucose234561 165432HCHOC OHC H HOC OH HC OH HCH2OH152346D-glucose (linear form) 11Fructose Ring Structures a 6-member pyranose ring, by reaction of the Cketo group with the OH on C6,or a 5-member furanose ring, by reaction of the Cketo group with the OH on C5. CH2OHC OC H HOC OH HC OH HCH2OHHOH2COHCH2OHHOHHHHOO165432654 321-fru to(linear) - -fru tofuranoeFructose may form either12MonosaccharidesSome examplesof pyranose ring structures for hexose sugars.The ring is not actually planar but exists in boat and chair conformers13Sugar DerivativesAn Amino sugar is a sugar in whichan amino group substitutes for a hydroxyl. An example is glucosamine. The amino group may be converted to an amide, as in N-acetylglucosamine. HOOHHOHHNH2HOHCH2OHH- -glucosamineHOOHHOHHN HOHCH2OHH- -N-acetylglucosamineC CH3OH14Anomers of GlucoseCyclization of glucose produces a new asymmetric center at C1. The stereoisomers are called anomers, & 0. Haworth projections represent the cyclic sugars as having essentially planar rings, with the OH at the anomeric C1: (OH below the ring) 0(OH above the ring). HOOHHOH HOHCH2OHH- -glucoseOHH HOOHHOH HOHCH2OHHHOH0- -glucose234561 16543215Glycosidic BondsThe anomeric hydroxyl groups of twosugars can join together, splitting out water to form a glycosidic bond. Two glucose molecules combine to form a disaccharide known as maltose.16HDouble sugarsGood source of energyBreak down into simple sugarsSucrose (glucose + fructose)Lactose (glucose + galactose)DisaccharidesOther disaccharides include: --Sucrose, common table sugar, has a glycosidic bondlinking the anomeric hydroxyls of glucose & fructose. -- Because the configuration at the anomeric C of glucoseis (O points down from ring), the linkage is (12). The full name of sucrose is -D-glucopyranosyl-(12)-0D-fructopyranose.)-- Lactose, milk sugar, is composed of galactose & glucose, with 0(14) linkage from the anomeric OH of galactose. Itsfull name is 0-D-galactopyranosyl-(1 4)--D-glucopyranose17H HCompare the structures of these three common disaccharidesDisaccharidesSucrose is an (1-4) link between D-Glucose and D-FructoseLactose is an (1-4) link between two D glucose18Examples:Starch- (plants) found in leaves, tubersGlycogen- (animals) found in the liver and musclesCellulose- (plants) make up cell walls3 or more sugars linked togetherComplex sugarsImportant for energy storageStarchPolysaccharides19 Plants store glucose as amylose or amylopectin. Both are glucose polymers collectively called starch. Amylose is a glucose polymer with (14) linkages. The end of the polysaccharide with an anomeric C1 that is not involved in a glycosidic bond is called the reducing end. Glucose storage in polymer form minimizes osmotic effects.Polysaccharides - Starches20Reducing endAmylose Amylopectin is a glucose polymer with mainly (14)linkages, but it also has branches formed by (16)linkages. Branches are generally longer than those shown in the diagram above. The branches produce a compact structure & provide multiple chain ends at which enzyme activity can occur.HOOHHOH HOHCH2OHHOHHOH HOHCH2OHHOH H HOOHOH HOHCH2HH HOHOH HOHCH2OHHOHH HOOHOH HOHCH2OHHOHO1 46HOHOH HOHCH2OHHH HOHOH HOHCH2OHHHO1OH3452amylopectinAmylopectin21Amylopectin Glycogen, the glucose storage polymer in animals, is similar in structure to amylopectin found in plants Glycogen has more (16) branches than amylopectin The ability to rapidly mobilize glucose is more essential to animals than to plants. The highly branched structure permits rapid glucose release from glycogen stores, e.g., in muscle during exercise. HOOHHOH HOHCH2OHHO HHOH HOHCH2OHHOH H HOOHOH HOHCH2HH HOHOH HOHCH2OHHOHH HOOHOH HOHCH2OHHOHO1 46HOHOH HOHCH2OHHH HOHOH HOHCH2OHHHO1OH3452glycogen Glycogen22GlycogenThe essential difference between amylose starch and cellulose is in the glycosidic link between the saccharide units.Amylose has l4) links.Cellulose has 0l4) links.Starch and Cellulose23CelluloseAmylose Cellulose is the major building component of plant cell walls Long chain of glucose molecules would be expected to be a great source ofenergy, but humans lack the necessary enzyme to digest cellulose The Endosymbiotic Protist in cow guts DOES have the enzymeCellulose24Dietary Fiber Dietary fiber is mainly plant material that is not hydrolyzed by enzymes secreted by the human digestive tract but may be digested by microflora in the gut. Examples of dietary fiber include cellulose, hemicellulose, lignin and pectin. Dietary fiber may be helpful in the prevention of conditions such as diverticulosis, irritable bowel syndrome, constipation, obesity, Crohns disease, hemorrhoids and diabetes mellitus. Carbohydrate Functions: Energy Sources During metabolism animals break down carbohydrates to carbon dioxide and water vapor. Monosaccharides and dissaccharides break down quickly and provide quick energy sources. Starches take longer to metabolize but the end products are the same. Human beings cannot break down cellulose, since we lack the appropriate enzyme to breakdown the 0 1-4 linkage26Carbohydrate Functions:Storage The main storage polysaccharides are starches and glycogen.While plants use starch as their storage polysaccharides, animals use glycogen. When the body has a high glucose concentration, the pancreas releases insulin, which converts glucose into glycogen and stores it in the liver. When the glucose concentration is low, the hormone glucagon converts glycogen back into glucose. Glycogen is the primary energy reserve in human beings . Metabolism of glucose provides the energy necessary for our bodies to function and carry out daily activities. When it is broken down into glucose and oxidized, ultimately to CO2and H2O, through cellular respiration, large amounts of energy are released.27Carbohydrate Functions: Structure Cellulose is a major component of plant cell walls.It is a polymer of0-D-glucose and forms a very strong fiber, which is excellent building material in plants. Cows and other ruminants have enzymes that break down cellulose. In humans it is primarily bulk or roughage. Chitin is a structural polysaccharide found in theexoskeletons of some insects. Chitin is a leather like structural substance that eventually hardens when it is shed. Chitin is often used in medicine for suturesbecause it is both strong and flexible, but it also decomposes over time. 28Carbohydrate Functions: Precursor Molecules Carbohydrates are precursors for the synthesis of certain biomolecules. Carbohydrates (ribose) form part of the skeletons of nucleic acids, DNA and RNA. The carbon skeletons of carbohydrates serve as raw material for the synthesis of other small organic molecules, such as amino acids and fatty acids. Disaccharides provide building material for structures that protect the cell or whole organism.29Digestive SystemDiverticular Disease Diverticulosis DiverticulitisDiverticulosisCommon disease with age Cause unknownPotential causes:ConstipationPressure caused by moving dry, hard bowel movementsDiverticula pouch-like projectionsDiverticulitisInflammation of the diverticulaMaterial caught in pocket causes inflammation, infectionand bleeding.Signs and Symptoms DiverticulosisMost people have no pain or symptoms Diarrhea Constipation Flatulence HeartburnSigns and Symptoms DiverticulitisTenderness Cramps Abdominal pain Infection Fever Nausea, vomiting Blood in the stoolWhat causes Diverticular Disease? Lack of fiber in diet weak areas form pouches Lack of exerciseControlling Diverticulosis Diverticulosis is different than diverticulitisHigh fiber diet Adds bulk and softens stoolsExercise or physical activity Check with doctor first! Low fiber (residue) diet initially Gradually increase fiber Low fat diet In severe cases only liquid diet or tube feeding may be necessary.Controlling DiverticulitisFollow a High FiberEating Plan Eat more fruits, vegetables, whole grains and beans Increase fiber gradually Drink plenty of waterCrohns Disease Crohns Disease Chronic inflammatoryChronic inflammatory condition of unknown etiology condition of unknown etiology Transmural inflammation Transmural inflammation Mouth to anus Mouth to anus Most commonly affects theMost commonly affects the ileum ileumCrohns DiseaseCrohns DiseaseCrohns disease is a chronic, unremitting,Crohns disease is a chronic, unremitting, incurable, inflammatory disorder thatincurable, inflammatory disorder that can affect the entire intestinal tract can affect the entire intestinal tractCrohns Disease and Ulcerative ColitisCrohns DiseaseThe End.46