Lecture 7- Carbohydrate chemistry (8/19) Flashcards
To be chiral an alcove must have ? sugars and a ketone must have? sugars
aldose 3
ketose 4
Glucose can cyclize to form a
Fructose can cyclize to form a
hemiacetal
hemiketal
What are anomers?
isomers of monosaccharides that differ only in their configuration about that asymmetric carbon
What are receding sugars?
sugars with a free anomeric carbon. They will reduce oxidizing agents such as peroxide, ferricyanide, and some metals.
Redox reaction convert sugars to ?
Sugar acids
Aldehydes and ketones
Is glucose a reducing sugar?
yes,
Formed by mild reduction of sugars
sugar alcohols
What are sialic acids ?
N-acetyl and N-glycolyl derivatives of neuraminic acid
Acetals can be formed from hemiacetals as a result of ?
Dehydration synthesis
Pyranose and furganose form of monosaccharides reacts with alcohols in dehydration synthesis to form ?
Glycosides
The new bond is called the glycosidic bond
Is sucrose a reducing sugar?
No
Starch and Glycogen are
Storage molecules
Chitin and cellulose and
structural molecules
The starch phosphorylase reaction claves glucose residues from amylose, producing
alpha -D-glucose-1-phosphate
Starch and glycogen consists of what kind of linkages?
alpha 1,4
Cellulose consists of what kind of linkages ?
Beta 1,4
amylose has what linkage
alpha 1,4
Cellulose strands are ? and chitin strands are ?
cellulose =parallel
chitins = can be parallel or antiparallel
2 carbons on chitin are
N-acetyl
One bilayer and thick peptidoglycan outer shell
Gram pos
Two bilayers and thin peptidoglycan shell in between the layers
Gram neg
pentaglycine bridge connects the tetra peptides
gram pos
direct amide bond between tetra peptides
gram neg
What unique amino acid was pointed out in the tetra peptide chain ?
isoglutamate
N-linked saccharides are attached via the?
Amide nitirugens of asparagine residues
O linked saccharides are attached to
hydroxy groups of serine , threonine or hydroxy lysine
Function of O-linked saccharides of glycoproteins
Adopt an extended conformation
-these extended conformations resemble “bristle brushes”
Bristle brush structure extends functional domains up out of the
glycocalyx
Function of N-linked oligosaccharides
alter chem and physical properties of proteins
stabilize protein
cleavage of units from N linked targets them for degradation in the liver
Progressive cleavage of what exposes Gal residues?
Sialic acid
Gal exposure increases liver binding
proteoglycans are glycoproteins whose carbohydrates are mostly ?
glycosaminoglycans
Linear chains of repeating disaccharides
glycosamineglycans
Glycosaminoglycans are composed of
proteoglycans
Serglycin and decorin are what type of protein?
soluble
syndecan is a ? protein
transmembrane
Forms the back bone structure of proteoglycans?
hyaluronate
proteoglycan consists of a core protein containing ?
O-linked and N-linked glycosaminoglycans
N-linked glycoproteins are of three types
high mannose, complex, and hybrid.
Hybrid - combines structure found in the complex and high mannose.
The carbohydrate groups of proteoglycans are predominantly
glycosaminoglycans )-linked to serine residues.
Function of proteoglycans ?
Modulation of cell growth process
Cushioning in joints
Carbohydrate formula
(CH2O)n
