Study guide 3 Flashcards
Whats the basic formula for saccharides
(CH2O)n where n ≥ 3
starch [α
1→4) glucose polymer]
What are the functions of carbohydrates?
- metabollic precursors
- energy metabolism and storage
- structural scaffolding for cell walls
- molecular recognition sites
Cellulose [β
[β(1→4) glucose polymer]
What are some of the chemical features of carbohydrates
linear and ring structures
extensive h-bonding
polymeric structures via glycosidic bonds (can be branched)
one or more chiral centers
How many carbon atoms des monosaccharides have
3-7 carbons
How is Monosaccharides classifed
number of carbons, nature of carbonyl group
What are the 2 carbonyl group in monosaccharides
aldose or ketose
Aldoses has how many carbons
more than or equal to 3 Carbons
In glucose, out of the 6 carbons, which ones are chiral
4 out of 6, n-2,has 2^ n-2 possible stereoisomers
In fructose, out of the 6 carbons how many are chiral
3 of them
Which form of monosaccharides are predominately in nature?
D-form sugars are predominate in nature.
How are D or L- orientation decieded
by the configurations of -OH at the C farthest from R-CO-R
Why are D-from sugars predominately in nature?
sterospecifity of enzymes
What are epimers
a pair of stereoisomers, diastereomers
Whats true about epimers
has a different configuration at only one of several stereogenic centers.
Which aldose stay monomer
glucose
The cyclization of sugars happen due to the reaction between
reaction between C5’ alcohol and carbonyl group (most reactive)
What is Pyranose derived from
Pyran
What is Furanose derived from
furan
How many carbons does a Pyranose ring have
6-membered ring
How many carbons does a Furanose ring have
5-membered ring
How are α and β anomers different from each other?
by the -OH configuration at anomeric carbon (C1 for aldoses; C2 for ketoses
What is the anomeric carbon for aldoses
C1
What anomeric carbon ketoses
C2`
α: −OH and highest carbon on the
opposite side (below the ring)
β: −OH and highest carbon on the
same side
α and β interconvert spontaneously via
via a linear intermediate (mutarotation)
Sugar conformations are
not flat
Which is more stable boat or chair conformations
chair is slighlty more stable than boat
What are some characteristics of sugar conformation?
sp3 hyb at Cs; 109.5º
What are the two sugar conformations
chair and boat conformation
Substituents can be located
equatorially or axially
Bilk substituents are more stable
equatorially
What is a glycosidic bond
a bond at the anomeric carbon
Glycosidic bond formation reaction occurs at
OH and anomeric carbon
Most polysaccharides have only how many reducing ends
1 reducing end
How are disaccharides named
names of monosaccharides involved + linkage type
Disaccharides are formed by
forming O-glycosidic bonds between monomers
What are the structures of polysaccarades
linear or branched
Which polysaccharide has a function of storage?
Starch and Glycogen
Which polysaccharide has a function of structure?
Cellulose and chitin
Which polysaccharide has a function of bacterial cell wall?
peptidoglycan
Recognation happens at the
cell surface
Why are polysaccharides needed for storage
keeps all monosacchrides and increases osmotic pressure
Osmosis depends on the
number of solute molecules, not the kind
Starch is the most
common storage polysaccharides in plants
Starch is a mixture of
glucose polymers
What is percentage of starch has α-amylose
20-25%
α-amylose characterstics
- left hand helix
- linear chains of 1000s of units with α(1→4) linkage
Amylopectin makes up, what percentage of starch
75-80%
Amylopectin characterstics
- liner chains with α(1→4) linkage AND branches at every 24-30 residues with α(1→6)
- 2x10 3 - 2x10 5 glucose units (largest polymers in nature)
α(1→4)
What is in saliva
amylase
What is the purpose of amylase in saliva
breaks some α(1→4) bond
What is in the small intestines
pancreatic amylase
What is in the mixture of pancreatic amylase
mixture of maltose and maltotriose (trisaccharides)
α-glucosidase sequentially removes
1 residue at a time at α(1→4)
β-glucosidase (debranching enzyme)
cuts α(1→6) linkages and α(1→4).
Glycogen is a storage polysaccharide in
animals
Where is Glycogen is prevalent where
in the liver (10%) and muscle (1-2%)
which one is more branched Glycogen or amylopectin
glycogen every 8-12 residue have α(1→6)
Glycogen can be
quickly metabolized and release glucose when blood sugar decreases
Glycogen phosphorylase cleaves
α(1→4) from nonreducing end.
Glycogen debranching
enzymes attack α(1→6) linkages.
Cellulose is the most
abundant natural ipolymer in nature
Cellulose role in Plant cell walls
rigidity and mechanical strentgh against osmotic stress
How many types of H-bond in cellulose
3
What are the 3 types of h-bonding in cellulose
intrastrand, interstrand, and intersheet
Why does cellulose have 3 types of h-bonding
very strong, insolube, and resistant to hydrolysis
chains in cellulose lie
side by side staggered to form sheets
Long linear polymer chain in cellose can be as long
as 15,000 units
Where is chitin located in
exoskeleton of crustaceans, insects and spider
what are the extended liner chains of chitin made of
N-acetyl-glucosamine (GlcNAc)
