Carbohydrates Flashcards Preview

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Flashcards in Carbohydrates Deck (26):
1

Most abundant class of biological molecules

Carbohydrates

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Monosaccharide

Smallest unit of carbohydrate structure
Empirical formula (CH2O)n, where n= 3-9 (5-6 common)

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Oligosaccharide

Polymers containing 2-20 monosaccharide residues

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Polysaccharide

Polymers that typically contain more than 20 residues

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2 types of monosaccharides

Aldoses (aldehydes)
Ketoses (ketones)

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Epimers

Stereoisomers that differ in configuration at only 1 chiral center

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Hemiacetal/hemiketal

Structure with hydroxyl group and ether at same carbon

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2 forms of cyclized rings

Furanose (5-membered)
Pyranose (6-membered)

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Alpha and beta anomeric positions in D-sugars

Alpha: trans to C6
Beta: cis to C6
L-sugars: switched

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Sugar phosphates

One of the carbohydrate's hydroxyl groups is converted to a phosphate ester

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Deoxy sugars

Hydrogen replaces the hydroxyl in the parent sugar

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Amino sugars

Amino group replaces a hydroxyl in the parent monosaccharide
Position of amino group is not always obvious, since it isn't numbered (but often carbon #2)

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Sugar alcohols

Carbonyl of parent sugar is reduced to an alcohol
Replace -ose with -itol

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Sugar acids

Either C-1 aldehyde is oxidized to carboxylic acid or primary alcohol (highest carbon number) is oxidized to an acid

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Disaccharides

Covalent linkage of 2 monosaccharides through a glycosidic bond at the anomeric carbon
Named in order with "free anomeric" sugar last
Glycosidic bonding is indicated using numbers separated by an arrow

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Reducing sugars

Sugars with an aldehyde or a hemiacetal can be oxidized to an acid and can reduce other ions

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2 types of polysaccharides

Homoglycans: 1 type of monomer
Heteroglycans: several types of monomers

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Amylose

Type of starch (storage polysaccharide)
Smaller than amylopectin and glycogen
Alpha- (1 -> 4) glycosidic linkages

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Amylopectin

Type of starch (storage polysaccharide and polymer of glucose)
Bigger than amylose, but smaller than glycogen
Amylose with alpha- (1 -> 6) branches every ~25 residues

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Glycogen

Form of storage used in most animals
Main chain is alpha- (1 -> 4)
Alpha- (1 -> 6) linkages every 8-12 residues
Bigger than amylose or amylopectin

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Cellulose

Linear polymer of glucose
Structural polysaccharide in plants
Unbranched, beta- (1 -> 4) glycosidic bonds
Highly rigid

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Chitin

Structural polysaccharide in bugs and crustaceans
Linear polymer of N-acetylglucosamine
Beta- (1 -> 4) glycosidic bonds

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Glycoconjugates

Polysaccharides covalently bound to proteins or peptides

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Proteoglycans

Complexes of proteins and glycosaminoglycans
High surface area: attract water for connective tissue

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Glycoproteins

Carbohydrates attached to proteins
Classified as N-linked (asparagine) or O-linked (serine)

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Peptidoglycans

Polysaccharides linked to small peptides
Found in the cell walls of many types of bacteria: keeps cell in rigid shape by maintaining osmotic balance