Bio: carbohydrates PP

flashcards

Empirical formula of carbohydrates

General formula (CH2O)n; carbohydrates are built from repeating CH2O units.

Carbohydrates

Functions include energy source/storage, structural components (cell walls/exoskeletons), and informational roles in cell signaling; can link to proteins and lipids.

Nomenclature of carbohydrates

Name based on the number of carbons plus the suffix -ose (e.g., triose for 3 carbons).

Aldose

Carbohydrate that contains an aldehyde group.

Ketose

Carbohydrate that contains a ketone group.

Monosaccharides

Simple sugars with 3–7 carbon atoms; all except dihydroxyacetone have one or more chiral centers.

Chiral carbon

Carbon atoms bounded to four different atoms or atom groups

Isomers

Compounds with the same molecular formula but different structures/properties; e.g., C6H12O6 isomers.

Enantiomers

Non-superimposable mirror-image isomers (D and L); most biological sugars are D, some are L (e.g., L-arabinose).

D- and L- stereoisomers

D isomers predominate in biology; L forms exist for some sugars.

Glucose

Most abundant monosaccharide; primary energy source; exists as a ring in solution; C6H12O6.

Glucose ring forms

Cyclization yields two anomers (alpha and beta) depending on the position of the –OH on C1.

Alpha anomer

Hydroxyl at C1 is opposite (trans) to the CH2OH group in the ring.

Beta anomer

Hydroxyl at C1 is on the same side (cis) as the CH2OH group in the ring.

Glycosidic bond

Covalent bond between two monosaccharides formed via an oxygen bridge (condensation).

Condensation

Reaction that links two sugars with release of water.

Hydrolysis

Bonds between sugars are broken by addition of water.

Disaccharide

Two monosaccharides linked by a glycosidic bond.

Sucrose

Glucose–fructose disaccharide with an α(1→2) glycosidic bond; hydrolyzes to glucose and fructose.

Lactose

Galactose–glucose disaccharide with a β(1→4) glycosidic bond.

Polysaccharides

Macromolecules made of repeating sugar units; important for energy storage and structural roles.

Starch

Plant storage polysaccharide of α-D-glucose; mainly α(1→4) linkages; exists as amylose and amylopectin.

Amylose

Linear component of starch; α-D-glucose units linked by α(1→4) bonds.

Amylopectin

Branched component of starch; α-D-glucose chains with α(1→6) branches.

Glycogen

Animal storage polysaccharide; highly branched α-D-glucose with α(1→4) chains and α(1→6) branches.

Cellulose

Structural polysaccharide of β-D-glucose with β(1→4) linkages; most abundant carbohydrate; plant fiber; humans cannot digest.

Chitin

Structural polysaccharide in arthropod exoskeletons; amino sugar derivative; supports fungal cell walls.

Glycoproteins

Proteins with attached carbohydrate moieties; about half of mammalian proteins; carbohydrates aid in recognition and signaling.

Glycolipids

Lipids with covalently bound oligosaccharide; essential for membrane surfaces and cell–cell interactions.