Carbohydrates Flashcards
What is the difference between an aldose and a ketose?
Aldose: Carbonyl group on C1
Ketose: Carbonyl group in internal carbon (usually C2)
What is an X-ose? (x = tri, tetr, pent, hex)
An aldehyde or a ketose with a certain number of carbons
How many stereoisomers do aldohexose and ketohexose have, and what does that mean for the number of chiral centres?
Aldohexose: 4 chiral centers, 16 stereoisomers
Ketohexose: 3 chiral centres, 8 stereoisomers
What is the difference between D- and L- glyceraldehyde?
D: OH on carbon 2 is on the right
L: OH on carbon 2 is on the left
What is the difference between enantiomers, diastereomers, and epimers?
Enantiomer: pair of nonsuperimposable mirror images
Diastereomer: pair non-mirror image stereoisomers
Epimer: diastereomers that are identical minus configuration at one chiral C
What is the difference between a hemiacetal and a hemiketal?
Hemiacetal: aldehyde + alcohol
Hemiketal: ketone + alcohol
How is glycopyranose formed?
C1 binds with OH of C5 to form a 6 membered ring
What are anomers?
Isomers that differ only at hemiacetal or hemiketal C in glucopyranose.
How is the alpha and beta glucopyranose anomers different?
Alpha: OH on C1 is on opposite sides of C6
Beta: OH on C1 is on the same side of C6
What is mutarotation?
Interconversion between alpha and beta anomers in glucopyranose, measured by the rotation of plane polarized light.
What is the difference in mutorotation of alpha and B glucose?
alpha: rotates light +112º
beta: rotates light +19º
Why is beta glucose more abundant than alpha glucose?
Beta-D-Glc can put bulky substituents in the equatorial position in its chair conformation.
What is glucitol?
Sugar derivative formed from the reduction (H gain) of the aldehyde on glucose to glycerol. (CH=O becomes CH2(OH))
How are monosaccharides reducing agents?
Linear aldoses give up the H (oxidation) on their aldehyde group to form a carboxyl group.
What are sugar phosphate esters?
Intermediates in sugar synthesis that prevent transport of sugar across membranes by adding phosphates in place of OH to “disguise” sugars.
What are amino sugars?
Intermediates in sugar synthesis that prevent transport of sugar across membranes by adding phosphates in place of OH to “disguise” sugars.
What are amino sugars?
Sguars that have an amide group replacing OH groups
What is a sugar amide?
compound formed when a sugar reacts with an amide group (-CONH₂). (e.g. N-acetylglucosamine.)
What is a deoxysugar?
Sugar in which the carbon 2 has two H2 bound instead of H and OH
What is an acetal and a ketal?
Non reducing, non mutarotating compound formed when a hemiacetal/hemiketal undergoes heated dehydration when reacted with an alcohol.
How is maltose made?
C1 of alpha glucose forms linear glycosidic bond with OH on C4 of another glucose
How is isomaltose formed?
C1 of alpha glucose forms a vertical glycosidic bond with the OH on C6 of another glucose.
what is the difference in formation of cellobiose and lactose?
Cellobiose: Glc(B1-4)Glc
Lactose: Gal(B1-4)Glc
How is sucrose made?
The C1 on alpha glucose forms a vertical glycosidic bond with the OH on C2 of beta fructose.
What makes a disaccharide reducing?
If it has a hemiketal or hemiacetal available to open up, linearize, and become oxidized.
What is invert sugar?
A mixture of glucose and fructose as a result of hydrolysis of sucrose. Called invert due to inversion from +66º rotation as sucrose to -39º rotation in the mixture.
how is trehalose made?
Glc(a1 - a1)Glc; non reducing, non mutorotating sugar used for energy storage in insects.
What are oligosaccharides?
Oligosaccharides are short chains of a few sugars. Important when attached to proteins or lipids on the outside of various animal cells.
What are some of the uses of oligosaccharides?
Cell-cell interactions in the nervous system, coating blood cells, ABO system
What are polysaccharides?
Long chains of sugar connected by the same kinds of glycosidic bonds (a1-4) or (b1-4). They play roles in storage of sugar and structure.
What is starch?
Storage form of D-Glc in plants. Include amylose and amylopectin.
What is the difference between amylose and amylopectin.
Amylose: long unbranched chains of a(1-4) that form a helix
amylopectin: chains of amylose linked by a(1-6) and does not form a helix.
What is glycogen?
Animal cell storage of Glc, similar to amylopectin but more branched.
What is dextrans?
Bacterial polysaccharides with a(1-6), and a(1-2), and a(1-4) links.
What is malting?
Enzyme-catalyzed hydrolysis that produced sugar for fermentation
What is cellulose?
Linear chain of many glucose units linked in D-cellobiose formed by B(1-4) linkkages. Strong rod like structure of parallel chains that undergo H bonding.
What is peptidoglycan?
Alternating B(1-4) linked N-acetylglucosamine and N-acetylmuramic acid sugars, cross linked by peptides. Form a 3 dimensional mesh like cell wall structure in bacteria cell walls.
what is a lysozyme?
enzyme that degrades bacterial cell walls by catalyzing the hydrolysis of B(1-4) linkages between N-acetylmuramic acid and N-Acetylglucosamine sugars in peptidoglycan
