arbohydrates - Introduction
arbohydrates - General Description A. Polyhydroxy Aldehydes or Ketones ARBN AIN B. Serve a variety of functions ARBN AIN ARBN AIN 1. Energy storage (Glucose, Glycogen, Starch) 2. Structural Support (ellulose, hitin) 3. Biochemical ontrol (DNA, Glycoproteins). ydrates of arbon - General formula: n(2)n, n=1,2,3... D. Saccharides - from Latin saccharum (sugar) 1. Monosaccharides - simple sugars 2. Disaccharides, trisaccharides, tetrasaccharides,... 3. ligosaccharides 4. Polysaccharides
arbohydrates - General Nomenclature A. -SE ending - Glucose, Galactose, Sucrose, ellulose B. lassification by Number of arbons 1. 363 - Tri + ose = Triose 2. 484 - Tetra + ose = Tetrose 3. 5105 - Penta + ose = Pentose. lassification by Functional Groups 1. Aldoses contain the aldehyde functional group. 2. Ketoses contain the ketone functional group. D. ombining A, B, and 2 an aldopentose 2 a ketohexose 2
arbohydrates - Simple Structures A. Simple Monosaccharide Structures D-Glyceraldehyde Dihydroxyacetone (A simple aldose) (A simple ketose) B. Note: Glyceraldehyde exists in two enantiomeric forms D
arbohydrates - Simple Structures A. Simple Monosaccharide Structures D-Glyceraldehyde Dihydroxyacetone (A simple aldose) (A simple ketose) B. Note: Glyceraldehyde exists in two enantiomeric forms D L
Stereochemistry - andedness in rganic ompounds Enantiomers - compounds that have the following characteristics: 1) Molecules of two compounds are mirror images of each other. 2) Molecules of two compounds are nonsuperimposable. The characteristics of enantiomers are often the result of a single chiral carbon atom.
hirality and ptical Activity hiral compounds exhibit a property called optical activity and are said to be optically active. Achiral molecules are optically inactive. ptical activity is the ability of a compound to rotate the plane of plane-polarized light.
hirality and ptical Activity
hirality and ptical Activity A chiral compound rotates the plane of plane-polarized light.
hirality and ptical Activity A sample tube containing an optically active compound is placed between the observer and plane-polarized light. An analyzing filter allows the observer to quantitate the degree to which the plane-polarized light is rotated.
ptical Activity - The Polarimeter
ptical Activity of Enantiomers ptical activity is the only property that distinguishes one enantiomer from the other. All other properties (MP, BP, solubility, etc.) are the same. D-Lactic Acid m.p. 53 o Very soluble in water [α] = - 2.6 o L-Lactic Acid m.p. 53 o Very soluble in water [α] = +2.6 o
Naming hiral ompounds 1) The two enantiomers of a pair of enantiomers rotate the plane of planepolarized light the same number of degrees but in opposite directions. 2) Rotation in the clockwise direction is called dextrorotatory ( + ) and in the anticlockwise direction, levorotary ( - ). 3) D- and L- are not directly related to (+) and (-), but are designations developed in carbohydrate chemistry to indicate a certain relationship between hydroxy groups. 4) When both the configuration and the optical rotation are known for a compound, both are indicated in the name: D-(+)-glyceraldehyde D-(-)-fructose 5) R- and S- designate specific relationship between atoms attached to a chiral carbon atom and are based on priority rules discussed in more detail in you text.
hiral Recognition Most reactions in living cells are catalyzed by protein molecules called enzymes. (Enzymes are a subset of a group of biological macromolecules referred to as receptors. ) Enzymes are large molecules containing a surface site, called the active site, where the substrate or reactant binds. For most enzymes this site is chiral. hiral active sites are designed to interact strongly with one of the two possible substrate enantiomers, just as a left shoe interacts strongly with a left foot, and more or less excludes a right foot. This phenomenon is called chiral recognition or chiral discrimination. ther molecular properties are also used by enzymes to discriminate between substrate molecules: geometrical isomerism, size, shape, polarity, and charge. Discrimination on these bases is called the complementarity principle.
hiral Recognition
hiral Recognition
hiral ompounds - Biological Activity
hiral ompounds - Biological Activity
arbohydrates - Simple Structures Important Aldopentoses Important Aldohexoses 2 2 D-ribose 2-deoxy-D-ribose 2 D-glucose 2 D-galactose Glucose and Galactose are epimers
arbohydrates - Simple Structures An Important Ketohexose 2 2 2 2 2 D-fructose D-glucose omparison of the structures of D-fructose and D-glucose D-fructose
arbohydrates - Simple Structures ow to remember them 2 2 2 2 2 2 D-glucose D-glucose D-galactose D-glucose D-fructose
arbohydrates - Simple Structures What is L-Glucose? D-Glucose and L-Glucose are enantiomers Most naturally occurring monosaccharides are from the D-series. 2 2 D-Glucose L-Glucose
Emil Fischer (1852-1919) 1902 Nobel Prize in hemistry
Absolute onfigurations of the D-Aldoses
Absolute onfigurations of the D-Ketoses
arbohydrates - yclic Structures Previously Studied Reactions of Aldehydes and Ketones
6 arbohydrates - yclic Structures 1 yclic Forms of Glucose 6 6 5 5 1 1 6 6 cyclic hemiacetal formation 6 5 5 1 1 anomers
arbohydrates - yclic Structures In solution, glucose exists in a variety of forms.
arbohydrates - Reducing Sugars Glucose is a reducing sugar u 2+ u2 The small amount of aldehyde present in a glucose solution is sufficient to reduce the copper ion from 2+ to 1+.
arbohydrates - yclic Structures yclic Forms of ther arbohydrates
arbohydrates - yclic Structures β-d-glucopyranose β-d-galactopyranose
arbohydrates - Reducing Sugars Because they exist to a small extent in the aldehyde form in solution, most other simple sugars are reducing sugars.
arbohydrates - Reducing Sugars Because they exist to a small extent in the aldehyde form in solution, most other simple sugars are reducing sugars.
arbohydrates - Glycoside Formation
Glycoside Nomenclature D methyl β glucopyranoside{
arbohydrates - Glycoside Formation The linkage between the sugar and the alcohol is called a glycosidic linkage and must be designated as α or β. Glycosides of simple monosaccharides are not reducing sugars because the aldehyde functional group is no longer present. The alcohol which attaches through the glycosidic can be another carbohydrate.
arbohydrates - Glycoside Formation
arbohydrates - Sugar Phosphates R P phosphate ester
arbohydrates - Acidic Sugars 2 α-d-glucose α-d-glucuronic Acid A building block for hyaluronic acid
arbohydrates - Amino Sugars 2 N 2 2 N 3 α-d-glucosamine N-acetyl-α-D-Glucosamine Building block for chitin, the exoskeleton of crustaceans
arbohydrates - Sugar Sulphates - S - 2 S N - α-d-glucuronic Acid 2-sulfate S - N-sulfo-α-D-Glucosamine 6-sulfate Building blocks for heparin
Monosaccharides - Physical Properties 1) Most monosaccharides are crystalline solids at room temperature and are very soluble in water where they can form highly viscous solutions. 2) Monosaccharides are slightly soluble in alcohols (methanol, ethanol) and are insoluble in less polar solvents (ethers, hydrocarbons). 3) Many monosaccharides taste sweet. 4) A solution of a reducing sugar may contain a mixture of α anomers, β anomers, and acyclic structures. The structures rapidly interconvert to form an equilibrium mixture. (This interconversion is called mutarotation.) 5) Usually, only a single form of a carbohydrate is drawn when drawing a carbohydrate in solution.
Mutarotation of Glucose alpha anomer oxo form beta anomer [α]d = +112º [α]d = +19º Equilibrium Mixture 36% 64% [α]d = +53º
Mutarotation of Glucose