Chapter 6: Sugars and Polysaccharides Flashcards
What are the basic units of carbohydrates
monosaccharides
How are monosaccharides synthesized
through gluconeogenesis
linking several monosaccharides results in
oligosaccharides
covalently linked monosaccharides result in
polysaccharides
monosaccharides contain at least ___ carbon atoms
3
they’re sp3 hybridized
If the carbonyl group on a monosaccharide is an aldehyde then it’s called
aldose
If the carbonyl group on a monosaccharide is a ketone then it’s called
ketose
define epimers
sugars that differ by only 1 carbon atom
What is the configuration of the farthest carbon if it has a D prefix?
the -OH group is on the right side
What is the configuration of the farthest carbon is it has an L prefix?
the -OH group is on the left side
What results from a reaction of an alcohol w/ an aldehyde
Hemiacetals
What results from a reaction of an alcohol w/ a ketone
Hemiketals
simple sugars can cyclize forming…
furanose
pyranose
In sugar ___ and ___ membered rings are most common due to greater stability
5 and 6
Are furanose and pyranose rings planar?
NO
they’re sp3 hybridized
In a pyranose ring OH in the ________ position are more reactive
equatorial
sugar acids are generated from
redox reactions
name the 3 types of sugar acids
- gluconic
- glucuronic
- glucaric
Gluconic acid forms from…
oxidation @ C1 position
Glucuronic acid form from…
oxidation @ C6 position
Glucaric acid forms from…
oxidation @ C1 & C6 positions
amino sugars contain
an amino group @ the C2 position
what are known as the simplest oligosaccharides
disaccharides
disaccharides are linked by a
glycosidic sugar bond
Any residue that has a free unsubstituted anomeric carbon is a
reducing sugar
a nonreducing end is identified by
the anomeric carbon
define anomeric carbon
the C1 carbon in a ring structure
Oligosaccharides occur widely as components of
antibiotics
give an example of an oligosaccharide
streptomyosin
what are longer chains of oligosaccharides
polysaccharides
polysaccharides are held together by
glycosidic bonds
glycosidic bonds are hydrolyzed by
glycosidases
define a homopolysaccharide
a polysaccharide that is composed of only 1 type of monosaccharide
define a heteropolysaccharide
a polysaccharide that is composed of many types of monosaccharides
polysaccharides function as….molecules
-storage
-structural
-recognition
give 2 examples of storage molecules
- starch
- glycogen
give two examples of structural molecules
- chitin
- cellulose
give an example of recognition molecules
- cell surface polysaccharides
what is a plant storage polysaccharide
starch
what are the 2 forms of starch
amylose
amylopectin
characteristics of amylose
- alpha 1,4 links
- 1 reducing end
branches in amylopectin are…
alpha 1,6
phosphorylase reaction releases
glucose-1-Phosphate
what is known as the “animal starch” and the storage device for energy in animals
glycogen
Does glycogen or amylopectin have more branching?
glycogen
changes the glucose linkages from 1,4 to 1,6 results in the formation of…
dextrans
do dextrans have branching? if so, where?
Yes
1,2
1,3
1,4
Cross-linked dextrans are used as
Sephadex 60
gel in column chromatography
what is the principle structural component of invertebrates
chitin
the C2 in chitin is
N-acetylated
NHC=OCH3
what is the primary structural component of rigid plant cell walls
cellulose
Cellulose and Chitin both contain what type of linkages
β 1,4
what is the most abundant natural polymer in the world?
cellulose
where is cellulose found?
- wood/bark
- plant’s cell wall
what is almost pure cellulose
cotton
both cellulose and chitin adopt a
fully extended “ribbon” conformation
amylose has what type of linkages
bent α
cellulose has what type of linkages
extended β
cellulose fibers have exceptional strength due to its
highly cohesive hydrogen bonded structure
Both cellulose and chitin form
hydrogen bonds
define ruminants
giraffes, cattle, deer, camels, buffalo
animals that can metabolize cellulose
How can ruminants metabolize cellulose?
b/c they have a bacterial cellulase in their rumen
rumen: large component in their stomach
cellulase is considered a
β (1,4) glucosidase
name 2 other structural polysaccharides
agarose
glycosaminoglycans
Glycosaminoglycans (GAGs) are linear chains of
alternating uronic acid and hexosamine residues
GAGs are known as what? why?
- ground substance
- b/c collagen & elastin are found embedded in this gel like substance
GAGs have a mucus-like consistency that results in
high viscosity and elasticity
Heparin is a natural
anticoagulant
Hyaluronates are components of
- vitreous humor of the eye & synovial fluid
- lubricant fluid of body’s joints
Chondroitin’s and keratin sulfate are found in
tendons & other connective tissues
dermatan sulfate is a component of the
ECM of the skin
GAGs are constituents of
proteoglycans
Glycoproteins are proteins that contain ______ chains ________ attached to their polypeptide side chains
oligosaccharide
covalently
most eukaryotic proteins exist as
glycoproteins
glycoproteins serve as
membrane receptors
immunoglobins
structural proteins
N-linked oligosaccharides contain an ____________ that is _________ to the amide nitrogen of an ________ residue
N-acetylglucosamine (NAG)
β -linked
asparagine (Asn)
O-linked oligosaccharides contain an _____________ that is _________ to the hydroxyl group of either ______ or _____ residues.
N-acetylglucosamine (NAG)
α-linked
serine
threonine
what is a diverse group of macromolecules that is found in the ECM between cells
proteoglycan
Can proteoglycans be cell membrane receptors? If so, give an examples.
Yes
syndecan
Proteoglycans consist of a core protein to which at least one…
glycosaminoglycan chain is covalently linked
What are the most common glycosaminoglycans found linked to the core protein of proteoglycans?
keratan sulfate
chondroitin sulfate
Describe syndecan
single transmembrane domain proteins
Syndecan are coreceptors that contain
heparan sulfate
chondroitin sulfate chains
Syndecan can bind to a variety of ______ including ____ and ____
ligands
VEGF
FGF
penicillin binds to and inactivates..
enzymes that cross-link peptidoglycan strands of bacterial cell walls
most bacteria that are resistant to penicillin secrete
penicillinase
how does penicillinase function?
by cleaving amide bond of β-lactam ring in penicillin
