Carbohydrates Flashcards
aldoses
carbohydrates that contain an aldehyde group
ketoses
carbohydrates that have a ketone group as their most oxidized functional group
Glycosidic linkages
sugars acting as substituents via this linkage are called glycosyl residues
Common names of monosaccharides
D- fructose, D-glucose, D-galactose, D-mannose
D-fructose is a ketose, rest are aldose
optical isomers/steroisomers
compounds that have the same chemical formula, differ in the spatial arrangement of their component atoms
Enantiomers
nonidentical, superimposable mirror images of each other (L glucose and D glucose)
Where is the OH in a D sugar?
On the right. “all D-sugars have the hydroxide of their highest number chiral center on the right”
Where is the OH in a L sugar?
On the left “all L sugars have the hydroxide of their highest number chiral center on the left”
What is the difference in an L and D glucose?
Every chiral center in the D-glucose has the opposite configuration of the L glucose
Diasteromers
two sugars that are in the same family, but are not identical and are not mirror images of each other
A diastereomer that differs in exactly one chiral center?
epimers
What is the most common electrophile on the MCAT?
A carbonyl group
What are cyclic hemiacetals formed from?
Aldoses
What are cyclic hemiketals formed form?
Ketoses
Pyranose?
Six member ring/saccharide with 5 carbons and one oxygen
Furanose?
5 member ring/saccharide
Anomeric carbon
The carbonyl carbon becomes chiral, will form an alpha or beta anomer
alpha-anomer
the OH group of C-1 is trans to the CH2OH substituent (A town down), axial and down
beta-anomer
the OH group of C-1 is cis to the -CH2OH substituent (equatorial and up)
mutarotation
exposing hemiacetal rings to water will cause them to spontaneously cycle between the open and closed form, making alpha and beta anomers
Aldonic acids
oxidized aldoses, aldehydes are oxidized to form catalytic acids
Any monosaccharide with a hemiacetal ring is considered?
a reducing sugar
When an aldose in a ring form is oxidized it yields a…?
Lactone–> a cyclic ester with a carbonyl group persisting on the anomeric carbon
ex. vitamin C
Tollens’ reagent
Helps detect a reducing sugar, AgNO3 is mixed with NaOH to produce a silver oxide (Ag2O), dissolved in ammonia to produce [Ag(NH3)2]+, the actual Tollens’ reagent
Benedict’s reagent?
The aldehyde group of an aldose is readily oxidized, indicated by a red precipitate of Cu2O.
(so benedict’s reagent is basically Cu++. It tests for reducing sugars, so sugars that can reduce Cu++ to Cu+. That means that the sugar becomes oxidized. Glucose is an aldehyde, so oxidizing the aldehyde gives you a carboxylic acid, or a carboxylate.)
Tautomerization
refers to the arrangement of of bonds in a compound, usually by moving a hydrogen and forming a double bond
ketone–> enol (OH with a double bond)
enol
a compound with a double bond and an alcohol group
alditol
when the aldehyde group of an aldose is reduced to an alcohol, the compound is considered an alditol
Deoxy sugar
contains a hydrogen that replaces a hydroxyl group on the sugar
Hemiacetals react with alcohols to form…?
acetals
will form glycosidic bonds and the acetals formed are glycosides
Glycosides derived from furanose rings are referred to as…?
furanosides
Glycosides derived from pyranose rings are called…?
Pyranosides
Sucrose
glucose - alpha 1,2 fructose
G-F
Lactose
galactose- beta- 1,4 glucose
Maltose
glucose- alpha- 1,4- glucose
Cellobiose
glucose- beta- 1,4 glucose
A polysaccharide composed entirely of glucose?
Homopolysaccharide
A polymer made up of more than one type of monosaccharide…?
Heteropolysaccharide
Celluose
main structural component of plants, homopolysaccharide, chain of B-D-glucose molecules linked by B-1,4 glycosidic bonds
Starches
polysaccharides that are more digestible by humans, linked alpha-D-glucose monomers, predominantly store starch as amylose; amylopectin is also a starch
Amylose
linear glucose polymer linked by alpha- 1,4 glycosidic bonds, how plants store starch
degraded by beta-amylase (cleaves off non-reducing end) while alpha-amylase cleaves randomly along the chain to yield shorter polysaccharide chains, maltose, and glucose
Amylopectin
has alpha- 1,4 glycosidic bonds, but also has alpha 1,6 glycosidic bonds
Glycogen
carbohydrate storage unit in animals, like starch but with more alpha-1,6 glycosidic bonds, highly branched
can be cleaved with glycogen phosphorylase
Glycogen phosphorylase
functions by cleaving glucose from the non-reducing end of a glycogen branch and phosphorylating it, thereby producing glucose-1-phosphate which plays an important role in metabolism
Phosphorylation
when a phosphate ester is formed by transferring a phosphate group from ATP onto a sugar
