Carbohydrates - Biochemistry Flashcards

Vocabulary-style flashcards covering key carbohydrate concepts from the lecture notes.

Monosaccharide

A carbohydrate that contains a single polyhydroxy aldehyde or polyhydroxy ketone unit.

Oligosaccharide

A carbohydrate that contains 2–10 monosaccharide units covalently bonded to each other.

Disaccharide

An oligosaccharide composed of two monosaccharide units covalently bonded.

Polysaccharide

A polymeric carbohydrate with many monosaccharide units covalently bonded; hydrolysis yields monosaccharides.

Glycosidic linkage

Bond between two monosaccharides formed from the reaction of a hemiacetal carbon with an –OH on another sugar; always a carbon–oxygen–carbon bond.

Aldose

A monosaccharide that contains an aldehyde functional group and is a polyhydroxy aldehyde.

Ketose

A monosaccharide that contains a ketone functional group and is a polyhydroxy ketone.

Triose

A monosaccharide with three carbon atoms.

Tetrose

A monosaccharide with four carbon atoms.

Pentose

A monosaccharide with five carbon atoms.

Hexose

A monosaccharide with six carbon atoms.

Pyranose

A cyclic monosaccharide containing a six-atom ring.

Furanose

A cyclic monosaccharide containing a five-atom ring.

Anomer

Stereoisomeric form of a cyclic monosaccharide arising from the new chiral center formed at the anomeric carbon during cyclization.

Alpha anomer

Anomer where the OH on the anomeric carbon is on a different side from the CH2OH group (opposite orientation in the cyclic form).

Beta anomer

Anomer where the OH on the anomeric carbon is on the same side as the CH2OH group.

Anomeric carbon

The carbon in a cyclic hemiacetal/hemiketal that was carbonyl in the open-chain form; new chiral center upon cyclization.

D-configuration

Monosaccharides whose highest-numbered chiral carbon’s CH2OH group is positioned according to the D-series (as determined by the lecture’s rule about CH2OH).

L-configuration

Monosaccharides whose highest-numbered chiral carbon’s CH2OH group is positioned opposite to the D-series.

Enantiomer

A pair of non-superimposable mirror-image stereoisomers.

Diastereomer

Stereoisomers that are not mirror images of each other; can include cis–trans isomers and molecules with multiple chiral centers.

Epimer

A diastereomer that differs at only one chiral center.

Chiral center

An atom (usually carbon) bonded to four different groups, giving handedness to the molecule.

Reducing sugar

A sugar that can reduce Tollens’ or Benedict’s reagents; aldoses are reducing sugars and, under basic conditions, some ketoses are as well.

Maltose

Disaccharide of two D-glucose units linked by an α(1→4) glycosidic bond; a reducing sugar.

Cellobiose

Disaccharide of two D-glucose units linked by a β(1→4) glycosidic bond; a reducing sugar.

Lactose

Disaccharide of galactose and glucose linked by a β(1→4) glycosidic bond; principal carbohydrate in milk; lactose intolerance due to lactase deficiency.

Sucrose

Disaccharide of glucose and fructose linked by an α(1→2) glycosidic bond; non-reducing sugar.

Starch

Storage polysaccharide in plants composed of amylose (linear, α(1→4)) and amylopectin (branched, α(1→4) and α(1→6)).

Amylose

Linear component of starch with α(1→4) glycosidic bonds.

Amylopectin

Branched component of starch with α(1→4) linked chains and α(1→6) branch points.

Glycogen

Animal storage polysaccharide; highly branched glucose polymer stored in liver and muscle.

Cellulose

Structural polysaccharide with β(1→4) linkages; linear and not digestible by humans due to lack of cellulase.

Chitin

Structural polysaccharide in arthropods and fungi, similar to cellulose but with N-acetylglucosamine and β(1→4) linkages.

Hyaluronic acid

Acidic polysaccharide with repeating N-acetylglucosamine and glucuronic acid; lubricates joints and ocular fluids.

Heparin

Anticoagulant acidic polysaccharide with repeating disaccharide units and sulfation.

Glycolipids

Lipids with covalently attached carbohydrate moieties; markers on cell membranes.

Glycoproteins

Proteins with covalently attached carbohydrate moieties; involved in cell recognition and signaling.

Glycemic index (GI)

A rating that indicates how quickly a carbohydrate-containing food raises blood glucose.

Dietary fiber

Indigestible polysaccharides (e.g., cellulose) that aid bowel movement; commonly 23–35 g/day recommended.

D-fructose

A ketohexose, also known as levulose or fruit sugar; sweetest natural sugar; found in fruits and honey.

D-glucose

Aaldose; primary energy source in humans; also called dextrose or grape sugar.

D-galactose

Epimer of glucose at C-4; component of lactose; used in glycoproteins and glycoprotein markers.

D-ribose

A aldopentose; component of RNA and ATP.