carbohydrates reviewer 222

polyhydroxy aldehydes or ketones.

In biochemical perspective, a carbohydrate is defined as

hydrates of carbon

Initially carbohydrates are referred to as ______ which follows stoichiometric formula (CH2O)n

Carbons - 3 Oxygen - 3 Hydrogen - 6

Glyceraldehyde and Dihydroxyacetone suggests that they have same number of atoms per element.

TAUTOMERS

Since Glyceraldehyde and Dihydroxyacetone only differ in functional groups, they are called

enediol intermediate

in organisms, tautomerization happens through an

CHIRAL or ASYMMETRIC carbons

Like most organic compounds, carbohydrates have

dextrorotatory (clockwise)

D means

levorotatory (counterclockwise)

L means

farthest from the carbonyl carbon

For carbohydrates with more than one chiralcenter, the D or L designation is determined by the hydroxyl group f…

D enantiomeric forms while L isomers are rare

In nature, the most abundant carbohydrates exist as

more chiral centers are formed..

As more carbons are added in a carbohydrate molecule,

NOT

Diastereomers are “ _ _ _ “ mirror images of each other.

2n stereoisomers

Generally, a molecule with n number of chiral carbon atoms will have _______ due to two possible position of hydroxyl group in each chiral carbon..

ANOMERS designated as alpha (OH below the ring) or beta (OH above the ring) conformation.

Cyclization results to formation of a NEW chiral center in carbon I, hence leading to formation of

or a five-membered closed structures which resembles pyran and furan rings

Sugars in ring conformation may adopt a six-membered

Haworth structures as proposed by the English chemist, Walter Haworth.

The ring form of carbohydrates are depicted by

Sugar Acids

Sugars with free anomeric carbon atoms are reasonably good reducing agents and will reduce hydrogen peroxide, ferricyanide, certain metals (Cu2+ andAg) and other oxidizing agents to form

(Fehling’s solution)

Alkaline CuSO₄

red Cuprous oxide (Cu₂O) precipitate

produces when Fehling’s solution is added with aldose sugar

Aldonic acid

Product formed when an aldose is oxidized (example: gluconic acid).

Uronic acids

Formed by oxidation of monosaccharides at C-6 (e.g., D-glucuronic, L-iduronic).

L-Iduronic acid

Same as D-glucuronic acid but with opposite configuration at C-5.

Aldaric acids

Produced when both C-1 and C-6 of a monosaccharide are oxidized (e.g., D-glucaric acid).

Sugar Alcohols

another class of sugar derivative, can be prepared by the mild reduction (with NaBH4 or similar agents) of the carbonyl groups of aldoses and ketoses.

Sugar Acids, Sugar Alcohols,

Deoxy Sugars, Sugar Esters, Amino Sugars

Types of monosaccharides derivatives:

–itol to the name of the parent sugar.

Sugar alcohols, or alditols, are designated by the addition of

The alditols are linear molecules that cannot cyclize in the manner of aldoses.

The alditols are linear molecules that cannot cyclize in the manner of aldoses.

Deoxy Sugars

Monosaccharides where a hydroxyl group is replaced by hydrogen. Example: 2-deoxy-D-ribose (2-deoxy-D-erythropentose).

Rhamnose

Found in ouabain, a toxic cardiac glycoside used as arrow poison.

L-Fucose and L-Rhamnose (both 6 deoxysugars) found in some cell walls.

are components of some cell wall.

Sugar Esters

Phosphate esters of glucose, fructose, and other monosaccharides are important metabolic intermediates

Ribose moiety of nucleotides

such as ATP and GTP is phosphorylated at the 5-position.

Amino sugars

Monosaccharides with an amino group at C-2 (e.g., D-glucosamine, D-galactosamine); found in chitin of insect and crustacean exoskeletons.

Muramic acid & Neuraminic acid

Modified glucosamines linked to three-carbon acids; components of cell membrane polysaccharides and bacterial cell walls.

Disaccharides

Carbohydrates composed of two sugar units joined by a glycosidic bond.

Maltose, Sucrose, Trehalose, Cellubiose, Gentibiose, Lactose

types of dissacharides:

Oligosaccharides

contain few monosaccharide units.

Polysaccharides

Carbohydrates composed of long chains of sugar molecules.

play significant roles in organisms as they serve as energy storage (glycogen and starch), provide structure (cellulose and chitin) as well as protection to host (bacterial cell wall of Gram positive bacteria).