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Chem 153A - Midterm 2 Exam With Complete
Solutions 100% 2026||Verified Exam!!!
What mechanism allows for the formation of cyclic
sugars? - Answers-cyclization (which is reversible)
allowing for mutarotation
cyclization is when the hydroxyl attached to C5 of the
straight chain monosaccharide attacks the anomeric
carbon (carbonyl); since the carbonyl is trigonal planar sp2
hybridization, the hydroxyl can attack from the front or
back, forming both alpha and beta anomers
What are anomers? How do they introconvert? - Answers-
Anomers are the alpha and beta forms of a cyclic sugar;
the distinguishing factor between them is whether the
alcohol group attached to the anomeric carbon is cis
(beta) or trans (alpha) to C6
They can introconvert because cyclization is a reversible
process, therefore the alcohol of C5 can nucleophilic
attack the anomeric carbon from the front or back,
producing both anomers
Be able to identify different anomers - Answers-Draw an
alpha and beta anomer for both L and D sugars
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Can a given sugar linearize and switch forms? When can't
it? - Answers-α- and β- forms of a given sugar can readily
"flip" between each form in solution, so long as the
anomeric hydroxyl is free
Be able to identify or create glycosidic bonds between
saccharides - Answers-Draw an alpha glycosidic bond,
beta glycosidic bond, and one that is both alpha and beta
For all four polysaccharides we've discussed, be able to
connect structure with function, and be able to recognize
any of these structures (structural support
polysaccharides) - Answers-Cellulose (plants): beta 1,4 -
glycosidic linkages; alternating structure where every other
glucose is inverted; this creates inter and intra-chain
hydrogen bonding which contributes to the straight chain
structure, allowing for stacked fibrils and creates high
tensile strength = good for structural support. Since beta
bonds can't be broken down by human enzymes, they are
not good for energy storage or utilization
Chitin (animals): beta 1,4 - glycosidic linkages, alternating
structure where every other glucose is inverted; this
creates inter and intra-chain hydrogen bonding which
contributes to the straight chain structure, allowing for
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stacked fibrils and creates high tensile strength = good for
structural support. Since beta bonds can't be broken down
by human enzymes, they are not good for energy storage
or utilization. Are comprised of N-acetyl-D-glucosamines
meaning that there are acetylated amine groups attached
to C2 instead of a hydroxyl group
For all four polysaccharides we've discussed, be able to
connect structure with function, and be able to recognize
any of these structures (energy storage polysaccharides) -
Answers-Amylose (plants): alpha 1,4 - glycosidic linkages;
can be broken down by human enzymes which makes
them good for energy storage and utilization; since the
structure does not have alternating glucose, there is no
interchain hydrogen bonding, so the structure of amylose
is helical and not as structurally sound with 8 glucose
residues per turn; is not branched
Glycogen: alpha 1,4 - glycosidic linkages AND alpha 1,6 -
glycosidic linkages every 8 to 10 glucose residues; can be
broken down by human enzymes which makes them good
for energy storage and utilization; since the structure does
not have alternating glucose, there is no interchain
hydrogen bonding, so structure is helical and not as
sound; branched = multiple pts of cleavage = faster
parallel breakdown; also good for storage because links
up monomers of glucose, reducing the amount of
Chem 153A - Midterm 2 Exam With Complete
Solutions 100% 2026||Verified Exam!!!
What mechanism allows for the formation of cyclic
sugars? - Answers-cyclization (which is reversible)
allowing for mutarotation
cyclization is when the hydroxyl attached to C5 of the
straight chain monosaccharide attacks the anomeric
carbon (carbonyl); since the carbonyl is trigonal planar sp2
hybridization, the hydroxyl can attack from the front or
back, forming both alpha and beta anomers
What are anomers? How do they introconvert? - Answers-
Anomers are the alpha and beta forms of a cyclic sugar;
the distinguishing factor between them is whether the
alcohol group attached to the anomeric carbon is cis
(beta) or trans (alpha) to C6
They can introconvert because cyclization is a reversible
process, therefore the alcohol of C5 can nucleophilic
attack the anomeric carbon from the front or back,
producing both anomers
Be able to identify different anomers - Answers-Draw an
alpha and beta anomer for both L and D sugars
,2|Page
Can a given sugar linearize and switch forms? When can't
it? - Answers-α- and β- forms of a given sugar can readily
"flip" between each form in solution, so long as the
anomeric hydroxyl is free
Be able to identify or create glycosidic bonds between
saccharides - Answers-Draw an alpha glycosidic bond,
beta glycosidic bond, and one that is both alpha and beta
For all four polysaccharides we've discussed, be able to
connect structure with function, and be able to recognize
any of these structures (structural support
polysaccharides) - Answers-Cellulose (plants): beta 1,4 -
glycosidic linkages; alternating structure where every other
glucose is inverted; this creates inter and intra-chain
hydrogen bonding which contributes to the straight chain
structure, allowing for stacked fibrils and creates high
tensile strength = good for structural support. Since beta
bonds can't be broken down by human enzymes, they are
not good for energy storage or utilization
Chitin (animals): beta 1,4 - glycosidic linkages, alternating
structure where every other glucose is inverted; this
creates inter and intra-chain hydrogen bonding which
contributes to the straight chain structure, allowing for
, 3|Page
stacked fibrils and creates high tensile strength = good for
structural support. Since beta bonds can't be broken down
by human enzymes, they are not good for energy storage
or utilization. Are comprised of N-acetyl-D-glucosamines
meaning that there are acetylated amine groups attached
to C2 instead of a hydroxyl group
For all four polysaccharides we've discussed, be able to
connect structure with function, and be able to recognize
any of these structures (energy storage polysaccharides) -
Answers-Amylose (plants): alpha 1,4 - glycosidic linkages;
can be broken down by human enzymes which makes
them good for energy storage and utilization; since the
structure does not have alternating glucose, there is no
interchain hydrogen bonding, so the structure of amylose
is helical and not as structurally sound with 8 glucose
residues per turn; is not branched
Glycogen: alpha 1,4 - glycosidic linkages AND alpha 1,6 -
glycosidic linkages every 8 to 10 glucose residues; can be
broken down by human enzymes which makes them good
for energy storage and utilization; since the structure does
not have alternating glucose, there is no interchain
hydrogen bonding, so structure is helical and not as
sound; branched = multiple pts of cleavage = faster
parallel breakdown; also good for storage because links
up monomers of glucose, reducing the amount of
