Structure and Function of Carbohydrates

Vocabulary flashcards summarizing major carbohydrate structures, classifications, reactions, and related biochemistry concepts.

Carbohydrate

Organic molecule with general formula Cn(H2O)n containing aldehyde or ketone groups and multiple hydroxyls.

Monosaccharide

Single-unit sugar; basic building block of carbohydrates (e.g., glucose).

Disaccharide

Carbohydrate composed of two monosaccharides linked by a glycosidic bond (e.g., sucrose).

Oligosaccharide

Carbohydrate containing 3–10 monosaccharide units.

Polysaccharide

Polymer of more than 10 monosaccharides; serves structural or storage roles (e.g., starch, cellulose).

Aldose

Monosaccharide whose carbonyl group is an aldehyde (–CHO).

Ketose

Monosaccharide whose carbonyl group is a ketone (>C=O).

Triose

Three-carbon monosaccharide.

Pentose

Five-carbon monosaccharide (e.g., ribose).

Hexose

Six-carbon monosaccharide (e.g., glucose, fructose).

D-Glucose

Aldohexose known as dextrose or blood sugar; primary energy source in humans.

D-Fructose

Ketohexose found in fruits; sweetest natural sugar.

D-Galactose

Aldohexose component of lactose; must be converted to glucose for metabolism.

D-Ribose

Aldopentose forming the sugar backbone of RNA.

Dihydroxyacetone

Simplest ketose; three-carbon ketotriose.

D-Glyceraldehyde

Simplest aldose; chiral aldotriose used to define D/L configuration.

Stereoisomer

Compounds with identical bonds but different spatial arrangements.

Enantiomer

Pair of non-superimposable mirror-image stereoisomers labeled D or L.

Chiral Center

Carbon atom attached to four different groups, giving rise to stereoisomerism.

Fischer Projection

Two-dimensional representation of carbohydrate stereochemistry with horizontal bonds projecting toward the viewer.

Haworth Projection

Planar ring depiction of cyclic sugars showing α/β orientation of the anomeric OH.

Anomer

Isomer differing at the anomeric carbon (α = OH down, β = OH up in D-sugars).

Mutarotation

Interconversion between α and β anomers in solution causing specific rotation change.

Reducing Sugar

Carbohydrate capable of reducing Cu2+ (e.g., in Benedict’s test) due to free aldehyde/ketone.

Benedict’s Reagent

Alkaline Cu2+ solution used to detect reducing sugars by color precipitate change.

Enediol

Intermediate with adjacent hydroxylated double-bond carbons formed under mild alkali, allowing aldose–ketose isomerization.

Phosphate Ester

Product of carbohydrate hydroxyl reacting with phosphoric acid (e.g., glucose-6-phosphate); formed by kinases.

Amino Sugar

Monosaccharide in which an OH is replaced by NH2 (e.g., glucosamine).

Glucosamine

β-D-2-aminoglucose; structural component of chitin, cartilage, and glycoproteins.

Glycosidic Bond

C–O–C linkage between the anomeric carbon of one sugar and an OH of another.

α(1→4) Linkage

Glycosidic bond connecting C1 (α) of one sugar to C4 of next (e.g., maltose, amylose).

β(1→4) Linkage

Bond between anomeric β-C1 and C4 of another sugar (e.g., cellulose, lactose).

Maltose

Disaccharide of two glucose units with α(1→4) bond; found in germinating grains.

Cellobiose

Glucose dimer with β(1→4) bond; humans lack enzyme to digest it.

Lactose

Milk sugar composed of β-D-galactose and either α- or β-D-glucose via β(1→4) bond.

Sucrose

Table sugar; α-glucose and β-fructose linked αβ(1→2); non-reducing.

Starch

Plant storage polysaccharide of α-D-glucose; mixture of amylose and amylopectin.

Amylose

Linear component of starch with α(1→4) glucosidic chains that coil.

Amylopectin

Branched starch component with α(1→6) linkages at branch points.

Glycogen

Animal storage polysaccharide similar to amylopectin but more highly branched.

Cellulose

Structural polysaccharide of plants; β(1→4) glucan forming strong fibers.

Mucopolysaccharide

Viscous polysaccharide (e.g., hyaluronic acid) composed of repeating disaccharide units for lubrication.

Hyaluronic Acid

Mucopolysaccharide of alternating N-acetylglucosamine and D-glucuronic acid with β(1→3) and β(1→4) links.

Peptidoglycan

Bacterial cell-wall polymer of N-acetylglucosamine and N-acetylmuramic acid cross-linked by peptides.

Glycoprotein

Protein covalently bonded to carbohydrate moieties involved in recognition, immunity, clotting, etc.

O-Linked Glycosylation

Attachment of sugars to the hydroxyl of serine or threonine residues via O-glycosidic bonds.

N-Linked Glycosylation

Attachment of carbohydrate to the amide nitrogen of asparagine side chains.

Dextrorotatory (+)

Optically active compound that rotates plane-polarized light to the right; common in D-sugars.

Levorotatory (–)

Compound rotating plane-polarized light to the left; often associated with L-isomers.