CarbohydratesSlide 2Types of CarbohydratesSlide 4Classification of MonosaccharidesMonosaccharidesSlide 7D and L Sugars and Fischer ProjectionsSlide 9Slide 10Slide 11D,L MonosaccharidesThree Important MonosaccharidesStructures of Glucose, D-Galactose and D-FructoseAmino SugarsCyclic Structures of MonosaccharidesCyclic StructureDrawing Haworth Structures for Cyclic FormsHaworth ProjectionsSlide 20Slide 21MutorotationChair ConformationsSlide 24Carbohydrates•Carbohydrates (or saccharides) consist of only carbon, hydrogen and oxygen•Carbohydrates come primarily from plants, however animals can also biosynthesize them•The “Carbon Cycle” describes the processes by which carbon is recycled on our planet- Energy from the sun is stored in plants, which use photosynthesis to convert carbon dioxide and water to glucose and oxygen- In the reverse process, energy is produced when animals oxidize glucose during respiration6CO2 + 6H2O + EnergyPhotosynthesisRespirationC6H12O6 + 6O2Simplified Carbon CycleTypes of Carbohydrates•Monosaccharides are the simplest carbohydrates- Also called “simple sugars”- Can’t be split into smaller carbohydrate units- Examples: glucose, fructose, galactose, ribose•Disaccharides are two monosaccharides bonded together- Can be split into two monosaccharides using an acid or enzyme catalyst- Examples: sucrose (table sugar), lactose (milk sugar)•Polysaccharides are polymers of monosaccharides- Used for storage of carbohydrates- Can be split into many monosaccharides with acid or enzymes- Examples: starch, cellulose, glycogen•monosaccharides have the general formula CCnnHH2n2nOOnn, where nn varies from 3 to 8Classification of Monosaccharides•Monosaccharides have 3-8 carbons in a chain, with one carbon in a carbonyl group, and the other carbons attached to hydroxyl groups- An aldose has the carbonyl C1 (an aldehyde)- A ketose has the carbonyl on C2 (a ketone)- The number of carbons is indicated as follows: triose (3 C’s), tetrose (4 C’s), pentose (5 C’s), hexose (6 C’s)CH2OHOCH2OHH OHH OHH OHCH2OHH OHCH2OHOHO HH OHH OHCH2OHOHHCH2OHH OH OGlyceraldehyde(aldotriose)Erythrulose(ketotetrose)Ribose(aldopentose)Fructose(ketohexose)Monosaccharides•Monosaccharides are classified by their number of carbon atomsHexoseHeptoseOctoseTrioseTetrosePentoseFormulaNameC3H6O3C4H8O4C5H1 0O5C6H1 2O6C7H1 4O7C8H1 6O8Monosaccharides•Fischer projection:Fischer projection: a two dimensional representation for showing the configuration of tetrahedral stereocenters–horizontal lines represent bonds projecting forward –vertical lines represent bonds projecting to the rearCHOCH OHCH2OHH OHCHOCH2OHconvert to a FischerprojectionD and L Sugars and Fischer Projections•Monosaccharides are chiral compounds (have stereoisomers)- Each monosaccharide has two enantiomeric forms•The D and L classifications are based on glyceraldehyde- Each enantiomer refracts plane-polarized light in equal magnitude but opposite direction- In glyceraldehyde, L rotates light to the left and D to the right (however, this is not true for all sugars)•L-glyceraldehyde has the hydroxyl group on the left, and D-glyceraldehyde has the hydroxyl group on the right- All other sugars are classified based on the position of the hydroxyl group farthest from the carbonyl:OHHCH2OHH OHO HCH2OHHOH OHH OHCH2OHH OHH OHHOHHOCH2OHHHOHOL-Glyceraldehyde D-GlyceraldehydeL-Ribose D-RiboseD,L Monosaccharides–the most common D-tetroses and D-pentosesCH2OHCHOOHOHHHCH2OHCHOOHHHOHHCH2OHCHOOHOHHOHHCH2OHCHOOHHHHOHHD-Erythrose D-ThreoseD-Ribose 2-Deoxy-D-riboseThree Important Monosaccharides•D-Glucose is the most common monosaccharide- Primary fuel for our cells, required for many tissues- Main sources are fruits, vegetables, corn syrup and honey- Blood glucose is maintained within a fairly small range- Some glucose is stored as glycogen, excess is stored as fat•D-Galactose comes from hydrolysis of the disaccharide lactose- Used in cell membranes of central nervous system- Converted by an enzyme into glucose for respiration (lack of this enzyme causes galactosemia, which can cause retardation in infants if not treated by complete removal from diet)•D-Fructose is the sweetest carbohydrate- Converted by an enzyme into glucose for respiration- Main sources are fruits and honey- Also obtained from hydrolysis of the disaccharide sucroseH OHHO HH OHH OHCH2OHH OHHO HHO HH OHCH2OHCH2OHOHO HH OHH OHCH2OHH OH OHHOOHHHHOHHOCH2OHHOD-Glucose L-Glucose D-Galactose D-FructoseStructures of Glucose, D-Galactose and D-Fructose•Note that in nature, only the D enantiomers of sugars are used•What is the relationship between D-glucose and L-glucose?•What is the relationship between D-glucose and D-galactose?•What is the relationship between D-glucose and D-fructose?(enantiomers, diastereomers and constitutional isomers)Amino Sugars•Amino sugars contain an -NH2 group in place of an -OH group –only three amino sugars are common in nature: D-glucosamine, D-mannosamine, and D-galactosamineCHOOHOHHNH2HHHOHCH2OHCHOOHOHHHHHHOH2NCH2OHCHOOHOHHNHCCH3HHHOHCH2OHOCHOOHHHNH2HHOHOHCH2OH42 D-Mannosamine(C-2 stereoisomer of D-glucosamineD-Glucosamine D-Galactosamine(C-4 stereoisomer of D-glucosamine)N-Acetyl-D-glucosamineCyclic Structures of Monosaccharides•Recall that an alcohol can react with an aldehyde or ketone to form a hemiacetal •If the alcohol and aldehyde or ketone are in the same molecule, a cyclic hemiacetal is formed•Monosaccharides in solution are in equilibrium between the open-chain and ring forms, and exist primarily in the ring form(Why does the 6-membered ring form, instead of a smaller one?)Cyclic Structure•Aldehydes and ketones react with alcohols to form hemiacetalshemiacetalsO-HHOCOOHHOO-HH4-Hydroxypentanal A cyclic hemiacetal1414redraw to show -OH and -CHO close to each otherDrawing Haworth Structures for Cyclic Forms•Step 1: Number the carbons in the chain and turn the Fischer projection of the open-chain form clockwise 90 degrees- Hydroxyl groups that were on the right are now on the bottom, and hydroxyl groups that were on the left are now on the top (they will stay on bottom or top in the Haworth structure)•Step 2: Rotate around so that C-6 sticks up from C-5, and the hydroxyl group on C-5 points towards C-1•Step 3: Form the cyclic hemiacetal by bonding the hydroxyl O to the carbonyl C and moving the hydroxyl H to the carbonyl O•Note: the cyclic hemiacetal has a new chiral