Uoft 2023 Fall BCH210 Final exam Questions
With Complete Solutions
Monosaccharide formula correct answer: (CH2O)n (n is 3 or
more)
Aldotriose correct answer: Also known as glyceraldehyde,
simplest aldehyde monosaccharide (n = 3), has L and D isomer
(centre carbon is chiral)
Ketotriose correct answer: Also known as dihydroxyacetone,
simplest ketone monosaccharide (n = 3), non chiral
Carbon numbering correct answer: Aldoses always have
aldehyde and C1, ketoses have ketone at C2
Sugar naming correct answer: triose, tetrose, pentose, hexose,
etc., l or d based on whether hydroxyl is right of chain (d) or left
(l), last chiral carbon (furthest from carbonyl) denoted with L or
D
L isomer of a sugar correct answer: Last chiral carbon's
hydroxyl is on the left
D isomer of a sugar correct answer: Last chiral carbon's
hydroxyl is on the right, found in body
Number of stereoisomers in a linear monosaccharide correct
answer: 2^(Number of chiral carbons), e.g. for an aldopentose,
,3 chiral carbons so 8 isomers, for a ketopentose, 2 chiral carbons
so 4 isomers. If including cyclic structures, there are 2 more or 4
more if it can form both 5 and 6 ring structures
cyclic structures of monosaccharides correct answer: Prevalent
form monosaccharides with 5 or 6 carbon atoms, form when the
hydroxyl group on the last chiral carbon reacts with the aldehyde
group or ketone group.
Furan ring correct answer: 5 member ring with O formed by
cyclization of a monosaccharide (cyclization of ketose usually).
Can occur with tetroses (4 Cs + O from carbonyl)
Pyran ring correct answer: 6 member ring with O formed by
cyclization of monosaccharide (cyclization of aldose usually)
Nucleophilic attack to cyclize sugars correct answer: Only
occurs in water, electrons of hydroxyl group attack carbonyl,
forming cyclic structure with the old hydroxide becoming an O
in the ring and a new hydroxide formed (using the old
hydroxide's H) either above/equatorial (beta) or below/axial
(alpha) the plane of the structure - beta is more stable
Anomeric Carbon correct answer: the new chiral center formed
in ring closure; it was the carbon containing the carbonyl in the
straight-chain form
Anomers correct answer: Isomers that differ at a new
asymmetric carbon atom formed on ring closure (e.g. alpha and
beta)
, Mutarotation correct answer: The rapid interconversion
between different anomers of a sugar that allows the substanace
to rotate polarized light
Isomers correct answer: Two different molecules that have the
same chemical formula
Constitutional isomers correct answer: same molecular formula,
different connectivity
Stereoisomers correct answer: Compounds with the same
structural formula but with a different arrangement of the atoms
in space.
Enantiomers correct answer: isomers that are mirror images of
each other
Diastereoisomers correct answer: Stereoisomers that are not
mirror images of each other. Includes epimers (only differ at one
assymetric carbon) and anomers (differ at a newly formed,
asymmetric C in the ring structure)
Reducing Sugars correct answer: Saccharides (sugars) that
donate electrons resulting in the reduction (gain of electrons) of
another molecule. Require a free OH next to O in the cyclic
form to convert back to the linear form and have a carbonyl to
react. Sugar acts as a reducing agent and is oxidized in reaction
Linearization of sugars correct answer: Bond is broken between
O and the carbon containing a hydroxyl. The O becomes a
With Complete Solutions
Monosaccharide formula correct answer: (CH2O)n (n is 3 or
more)
Aldotriose correct answer: Also known as glyceraldehyde,
simplest aldehyde monosaccharide (n = 3), has L and D isomer
(centre carbon is chiral)
Ketotriose correct answer: Also known as dihydroxyacetone,
simplest ketone monosaccharide (n = 3), non chiral
Carbon numbering correct answer: Aldoses always have
aldehyde and C1, ketoses have ketone at C2
Sugar naming correct answer: triose, tetrose, pentose, hexose,
etc., l or d based on whether hydroxyl is right of chain (d) or left
(l), last chiral carbon (furthest from carbonyl) denoted with L or
D
L isomer of a sugar correct answer: Last chiral carbon's
hydroxyl is on the left
D isomer of a sugar correct answer: Last chiral carbon's
hydroxyl is on the right, found in body
Number of stereoisomers in a linear monosaccharide correct
answer: 2^(Number of chiral carbons), e.g. for an aldopentose,
,3 chiral carbons so 8 isomers, for a ketopentose, 2 chiral carbons
so 4 isomers. If including cyclic structures, there are 2 more or 4
more if it can form both 5 and 6 ring structures
cyclic structures of monosaccharides correct answer: Prevalent
form monosaccharides with 5 or 6 carbon atoms, form when the
hydroxyl group on the last chiral carbon reacts with the aldehyde
group or ketone group.
Furan ring correct answer: 5 member ring with O formed by
cyclization of a monosaccharide (cyclization of ketose usually).
Can occur with tetroses (4 Cs + O from carbonyl)
Pyran ring correct answer: 6 member ring with O formed by
cyclization of monosaccharide (cyclization of aldose usually)
Nucleophilic attack to cyclize sugars correct answer: Only
occurs in water, electrons of hydroxyl group attack carbonyl,
forming cyclic structure with the old hydroxide becoming an O
in the ring and a new hydroxide formed (using the old
hydroxide's H) either above/equatorial (beta) or below/axial
(alpha) the plane of the structure - beta is more stable
Anomeric Carbon correct answer: the new chiral center formed
in ring closure; it was the carbon containing the carbonyl in the
straight-chain form
Anomers correct answer: Isomers that differ at a new
asymmetric carbon atom formed on ring closure (e.g. alpha and
beta)
, Mutarotation correct answer: The rapid interconversion
between different anomers of a sugar that allows the substanace
to rotate polarized light
Isomers correct answer: Two different molecules that have the
same chemical formula
Constitutional isomers correct answer: same molecular formula,
different connectivity
Stereoisomers correct answer: Compounds with the same
structural formula but with a different arrangement of the atoms
in space.
Enantiomers correct answer: isomers that are mirror images of
each other
Diastereoisomers correct answer: Stereoisomers that are not
mirror images of each other. Includes epimers (only differ at one
assymetric carbon) and anomers (differ at a newly formed,
asymmetric C in the ring structure)
Reducing Sugars correct answer: Saccharides (sugars) that
donate electrons resulting in the reduction (gain of electrons) of
another molecule. Require a free OH next to O in the cyclic
form to convert back to the linear form and have a carbonyl to
react. Sugar acts as a reducing agent and is oxidized in reaction
Linearization of sugars correct answer: Bond is broken between
O and the carbon containing a hydroxyl. The O becomes a
