lecture ten - carbohydrates Flashcards
monosaccharides
basic building blocks from which all carbs are constructed
have one monomer unit
aldose monosaccharides
aldehyde functional group
ketose monosaccharides
ketone functional group
oligosaccharides
2-10 units
disaccharides
specific type of oligosaccharides that have 2 units
polysaccharides
have more than 10 units, up to 1000+
D vs L sugar
D glucose rotates plane-polarized light clockwise
L glucose rotates plane-polarized light counterclockwise
isomer of the most naturally occurring carbohydrates
D-isomer
configuration
the 3D arrangement of substituent groups around a chiral center; relates to carbs because they are either D or L isomers based on what their substituent arrangement is
conformation
spatial arrangements of a molecule resulting from free rotation about the carbon-carbon single bonds
epimer
monosaccharides that differ in stereochemistry at only one chiral carbon
why do most epimers have different chemical names?
because they are two different chemicals with different chemical reactivities
glucose
simple sugar
fructose
simple sugar, found in many plants, often bonded with glucose to from sucrose
galactose
simple sugar, usually found combined with other sugars
mannose
important in human metabolism
ribose
monosaccharide that is used in RNA
deoxyribose
monosaccharide found in DNA
N-acetyl-glucosamine
monosaccharide derivative of glucose; amide between glucosamine and acetic acid, important in bacterial cell wall
N-acetyl-galactosamine
amino sugar derivative of galactose; in humans, it’s the terminal carb forming the antigen of blood type A
maltose
disaccharide made of two glucose units, often used in fermentation, linked with 1-4 bond
isomaltose
made of maltose, linked with 1-6 bond
lactose
disaccharide made of glucose and galactose, often found in dairy products
cellobiose
disaccharide consisting of two glucose units in beta glycosidic linkage; obtained from partial hydrolysis of cellulose
sucrose
nonreducing disaccharide made of glucose and fructose
amylose
D-glucose units bonded by α-1,4 glycosidic bond, make up starch
glycogen
storage carb, α-1,4 and 1-6 linkages
cellulose
no taste, not digestible, found in plant cell walls
mutarotation
equilibration between alpha and beta anomers through the open-chain form
results in alpha and beta anomers because when the compounds become cyclic, they become either alpha or beta anomers
hemiacetals
alcohol and aldehyde group reacted together on the same molecule; formed through the cyclization of an aldose
acetal
formed from reaction of a second alcohol molecule with a hemiacetal
defining characteristic of a reducing sugar
can mutarotate through the open chain form to produce an aldehyde
why are monosaccharides reducing sugars but methylated derivatives (at the anomeric carbon) not reducing sugars?
because methylated derivates become locked in acetal structure which doesn’t allow them to mutarotate
most bulky substituents are located…
equatorial positions
deoxy-sugars
lack a hydroxyl group at one of their carbons
sugar phosphates
at least one covalently bound phosphate residue
sugar acids
contain at least one carboxyl group
sugar alcohols
aldehyde or ketone group is replaced by additional hydroxyl group
amino sugars
have amino group substitutes for one hydroxyl group
N-acetyl derivates of glucose and galactose
very common components of proteoglycans and glycoproteins
what is an N-glycosidic bond and in what compounds are these bonds found?
nitrogen atom of an organic base (purine or pyrimidine) is covalently linked to the anomeric group of ribose or deoxyribose
these bonds are found between monosaccharides to form oligo and polysaccharides
o-glycosidic bonds
link different sugars together to form di, oligo, and polysaccharides
difference between an alpha and beta glycosidic bond
alpha linkage happens when the linkage from anomeric carbon radiates in the downward direction
beta linkage occurs when the linkage from the anomeric carbon radiates in an upward direction
human storage of polysaccharide
glycogen; contains 90% alpha 1-4 linkages and 10% alpha 1-6 linkages
glucose
units in glycogen that form a spiral structure, digestible by humans
enzymes act of what ends of glycogen
non-reducing ends, facilities its rapid synthesis and catabolism
nucleotide sugar
something that helps synthesize carbohydrate polymers from monomers
synthesis of carb polymers by catalysis
catalyzed by enzymes called glycotransferases
synthesis of carb polymers from monomers
accomplished by a variety of nucleotide sugars
cleavage of phosphoester linkages
drive the process in direction of polysaccharide
major human blood types
A, B, O
blood types are named after antigens that are found on the surface of the red blood cells, and these antigens are simple chains of sugars
they are carbohydrates found on cell surfaces, attached to proteins and lipids
