chapter 15

Anomer

A carbon cyclic hemiacetal that has the option of being alpha or beta based on the location of the alcohol on the anomeric carbon

Anomeric carbon

Carbon 2; not chiral, but it determines whether the molecule is alpha or beta

Carbohydrates function

Stereochemistry,

Carbohydrate types

Monosaccharides, oligiosaccharides, polysaccharides

Stereoisomers

Isomers that have the same connectivity but a different orientation of their atoms in space

Enantiomers

Non-super impossible mirror images, refers to relationship b/w pairs of objects

Chiral

Handedness, an object that is not on its mirror image, enantiomers have at least one chiral carbon

D- and L- nomenclature

D compounds have -oh on the penultimate carbon on the right side

L compounds have -oh on the penultimate carbon on the left side

Configurations relative to D-glyceraldehyde

Molecules are sometimes numbed by their relation to glyceraldehyde

Diastereoisomers

Non mirror images

Meso compounds

superimposable mirror images

Racemic mixtures

with equal concentrations of two enantiomers, will not be optically active because the two enantiomers' rotations cancel each other out

Carbohydrates

Most abundant organic compounds in the plant world, 3/4 of dry weight of plants, good energy sources, compounds of supportive tissue

Types of carbohydrate

Classified by # of sugar units in total chain

-saccharides

Mono- one

Dia-two

Oligio-two-ten

Poly- ten+

How are sugar units connected?

By glycoside bonds or oxygen atom bridges

Monosaccharide names

Tri- 3, tetra-4, penta-5, hex-6, so on…

Monosaccharides differ by

of carbon atoms, ketose/aldhose, stereochemistry

D-glyceraldehyde

Simplest of all sugars, only one chiral center, configurational standard for other carbohydrates (D- or L-)

D-glucose

Glucose is an aldohexose sugar, common names: sugar, dextrose, grape sugar, blood sugar; most important in our diet, most abundant in nature, level in blood can be 0.1% (104 mg/dL)

6 c's, 3rd c is ALWAYS OH on the L

D-fructose

Another common sugar, ketohexose, sweetest of all natural sugars, 6 c's, 3rd c is ALWAYS on the L

D-galactose

Not found in many biological systems, common part of lactose disaccharide, converts ingested galactose to glucose

D-ribose

Sugar in genetic material, not used as energy source but is part of the RNA, c-2 OH is removed to make deoxyribose

Intramolecular cyclization of carbohydrates

Many form intermolecular hemiacetals, aldehydes and ketones form hemiacetals and hemiketals when reacted with alcohol

6 member Ed cyclic carbohydrates are called

Pyranoses

5 membered hemiketals are called

Furanoses

Hayworth projections

Created by Nobel prize winner, cyclic structures depicted by 3d drawing adhering to a set of rules, carbon atoms not explicitly drawn, sometimes hydrogen not drawn, ring is perpendicular to paper, darkened line projects toward reader

Mutarotation of D-glucose

A and b are anomeric are in eq so one can convert to another mutarotation

Mutarotation of D-fructose

A and B are anomeric in eq so they can convert to another mutarotation

Monosaccharide physical properties

Colorless, crystalline solids, they can hydrogen bond w water so they are highly soluble in water, slightly soluble in nonpolar solvents (benzene, diethyl ether)

Monosaccharides rxns

Methyl groups added to the 2nd carbon's OH

Reducing sugars

Aldehyde groups are oxidized by Benedict's reagent, measures glucose in urine

What sugars are reducing sugars?

All monosaccharides and all common disaccharides (excluding sucrose)

Diasaccharides

2 monosaccharides in carbohydrates, connect by glycosidic bond b/w anomeric carbons

Lactose

Milk sugar, d-glucose + d-galactose, intolerance comes from lack of lactase to hydrolyze the glycosidic link of lactose

Sucrose

D-glucose + d-fructose

Polysaccharides

Contain large #s of monosaccharide chains, 3 cat's

storage polysaccharides

Energy storage; starch, glycogen

Structural polysaccharides

Protective walls w/ lubractive coating; cellulose, mucopolysaccharides

Structural peptides

Bacterial cell walls

Starch

Energy shortage for plants, contains long a-d-glucose chains, up to 4000 units, combination of amylose and amylopectin

Amylose

Straight-chained starch; a(1->4) glycosidic bond + a-d-glucose

Amylopectin starch

Branched chain, a(1->6) glycosidic bonds to to amylose chain, every 24-30 chains

Cellulose

Most abundant polysaccharide, cell-wall material of wood, b(1->4) glycosidic bonds, 2200 units in length, cannot metabolize cellulose as we do not have enzymes to catch the hydrolysis of b-glycoside bonds

Glycoside

Major glucose storage carb in animals, hughtl branched chain like amylopectin, 10 monomers, stored in liver + muscle