Chapter 11. Carbohydrates Flashcards
Molecules that have identical molecular formulas but differ in how the atoms are ordered. For instance, glyceraldehyde and dihydroxyacetone.
Constitutional isomer
The study of the glycome, all of the carbohydrates and carbohydrate-associated molecules that cells produce. Like the proteome, the glycome is not static and can change, depending on cellular and environmental conditions.
Glycomics
a monosaccharide whose C-1 carbon contains an aldehyde group.
Aldose
A pair of molecules, each with more than one asymmetric center, that have opposite configurations at one such center but are not mirror images of each other; in the aldotetrose series, Derythrose and D-threose are diastereoisomers.
Diastereoisomer
Reactions between an amino group in a protein not participating in a peptide bond and the aldehyde form of a carbohydrate. Such reactions frequently compromise protein function.
Advanced glycosylation product
isomers of cyclic hemiacetals or hemiketals, with different configurations only at the carbonyl carbon; that carbon is known as the anomeric carbon.
Anomer
an unbranched homopolysaccharide in plants, composed of glucose residues in α-1,4 linkage; the major structural polysaccharide in plants.
Cellulose
Consists of two sugars joined by an O-glycosidic bond.
disaccharide
The study of the synthesis and structure of carbohydrates and how carbohydrates are attached to and recognized by other molecules such as proteins.
Glycobiology
single aldehydes or ketones that have two or more hydroxyl groups; the simplest carbohydrates.
Monosaccharide
pairs of molecules with one or more chiral centers that are mirror images of each other.
Enantiomer
a monosaccharide that has a ketone group as its most oxidized carbon.
Ketose
a six-membered heterocyclic ring formed when a monosaccharide cyclizes to form a hemiacetal or a hemiketal; the six-membered, oxygen-containing ring is similar to that of pyran.
Pyranose
a five-membered heterocyclic ring formed when a monosaccharide cyclizes to form a hemiacetal or a hemiketal; the five-membered oxygen-containing ring is similar to that of furan.
Furanose
pairs of molecules with more than one asymmetric center that differ in configuration at only one such center; glucose and galactose are epimers, differing only in the configuration at C-4.
Epimer
A readily mobilized storage form of glucose in which the glucose monomers are linked by α-1,4-glycosidic bonds and with branches (α-1,6-glycosidic bonds) at about every tenth residue.
Glycogen
Forms of a specific protein that differ only in patterns of glycosylation.
Glycoform
A protein that binds specific carbohydrate structures on neighboring cell surfaces.
Glycan-binding protein
an extensive system of cytoplasmic membranes that comprises about half the total cell membrane. The region of the ER that binds ribosomes is called the rough ER while the region that is devoid of ribosomes is called the smooth ER.
Endoplasmic reticulum
proteins that have a specific carbohydrate moiety attached.
Glycoprotein
a lipid containing approximately 20 isoprene units that serves as a carrier of oligosaccharides destined to be attached to a protein, through a membrane.
Dolichol phosphate
a compound formed by the reaction of an aldehyde functional group and a hydroxyl group; for example, the C-1 group of the open-chain form of glucose reacts with the C-5 hydroxyl group to form an intermolecular hemiacetal.
Hemiacetal
carbohydrate composed of 2 to 10 or 12 monosaccharide units.
Oligosaccharide
sugars that convert to a form with a free aldehyde group that is readily oxidized, thus reducing another compound.
Reducing sugar
a covalent bond between an aldehyde or ketone function of a monosaccharide and an oxygen, nitrogen, or sulfur atom of another molecule. The most common glycosidic linkages are O-links between the anomeric carbon of a sugar and a hydroxyl group of another saccharide.
Glycosidic bond
sugars that are not readily converted to a form with a free aldehyde group capable of reducing another compound. Such a conversion is prevented because the sugar forms a glycosidic bond with another compound.
Nonreducing sugar
carbohydrates composed of large numbers of linear or branched monosaccharide units; homopolysaccharides are composed of large numbers of one type of sugar, while heteropolysaccharides contain more than one type.
Polysaccharide
a compound formed by the reaction of a ketone group and a hydroxyl group; for example, the C-2 keto group of the open-chain form of fructose reacts with the C-5 hydroxyl group to form an intermolecular hemiketal.
Hemiketal
any one of a number of specific enzymes that catalyze the formation of glycosidic bonds.
Glycosyltransferase
A glycoprotein that is predominately carbohydrate. N-Acetylgalactosamine is usually the carbohydrate moiety bound to the protein in mucins, which serve as lubricants.
Mucin (mucoprotein)
a heteropolysaccharide made of repeating disaccharide units and containing the amino sugar glucosamine or galactosamine.
Glycosaminoglycan
plant proteins with a high affinity for specific sugar residues. As such, they are important probes of carbohydrate containing molecules.
Lectin
a stack of membranous sacks in the cytoplasm which is the major sorting center for proteins which reside in cell membranes and the lumen of organelles.
Golgi complex
proteins containing one or more covalently linked glycosaminoglycan chains. Cartilage proteoglycan contains keratan sulfate and chondroitin chains linked to a polypeptide backbone.
Proteoglycan
a homopolysaccharide that is a storage form of glucose in plant chloroplasts; amylopectin, the branched form of starch, has approximately one α-1,6 linkage per thirty α-1,4 linkages, while amylose is unbranched, composed of glucose residues in α-1,4 linkage.
Starch
carbohydrate-binding proteins that constrain immune-system cells to the site of injury in the inflammatory response.
Selectin
Isomers in which the atoms are connected in the same order but differ in spatial arrangement.
stereoisomer
