sucrose - ANSWER-glucose + fructose with a glycosidic bond
simple monosaccharide - ANSWER-formula: (CH2O)n
-simplest carbohydrates
-have an aldehyde or ketone group
sugars with a aldehyde have a prefix aldo-
sugars with a ketone group have a prefix keto-
-if a ketose, the ketone group is alwa...
BCH210 Exam Questions| Already
Answered| GRADED A+
sucrose - ANSWER-glucose + fructose with a glycosidic bond
simple monosaccharide - ANSWER-formula: (CH2O)n
-simplest carbohydrates
-have an aldehyde or ketone group
sugars with a aldehyde have a prefix aldo-
sugars with a ketone group have a prefix keto-
-if a ketose, the ketone group is always at carbon 2- this decreases the amount of isomers that could
form
-made up of chiral carbons- allowing the sugars to form different isomers, leading to structural diversity
(aldose could form more because they have more chiral carbons)
-aldehyde and ketone groups are reactive which allow them to cyclize (formation of 2 additional
structures- beta or alpha). this also means that they are reducing sugars when they react with oxidizing
agents
carbohydrate numbering and configuration - ANSWER-a sugar with an aldehyde- start counting the
carbons at the aldehyde group (ie aldehyde is c1)
a sugar with a ketone- ketone is always at C2 count based on that
-each chiral carbon could form 2 possible isomers, d or l
-aldehydes and ketones are either D or L isomers
based on the orientation of the OH on the chiral carbon furthest from the aldehyde or ketone group
-D isomer= OH on the right
-L isomer=OH is on the left
-D sugars are biologically important- L isomers are found in bacteria
-D or L isomers could be alpha or beta when cyclized
,to calculate the number of possible linear steroisomers, 2^x where x= number of chiral carbons that
could isomers
carbohydrate cyclization - ANSWER--intramolecular reaction that takes place within the sugar molecule
that coverts the sugar from linear to cyclic form in solution (in solution this reaction is reversible)
-possible because the functional group of the sugar (OH, aldehydes and ketone) is very reactive
-the aldehyde or ketone carbonyl undergoes a nucleophilic attack by the farthest hydroxyl group from it
to form a cyclic structure
-reactions for a member furan ring or 6 member pyran ring
-the Oxygen in the cyclized form comes from the hydroxyl that attacked the ketone or aldehyde
-the chirality of cyclic structures can be detected by mutarotation, a change in the optical rotation of
polarized light following the interconversion between the alpha and beta anomer. this is how we could
measure how much beta and alpha rings there is in solution based on how the polarized light is being
rotated
The new bond may be:
-hemiacetal: aldehyde derivative (OH attacking an aldehyde)
-hemiketal: ketone derivative (OH attacking a ketone)
-final product is an alpha when the hydroxyl is below the Oxygen or a beta when the hydroxyl is above
-the beta structure is more stable because the OH are opposite from each other (less repulsion).
Because of this, more would be found in solution.
fructose - ANSWER-can form a furan ring and pyran ring
-main sugar found in honey
carbs modification - ANSWER-sugars can be phosphorylated, methylated or N-containing functional
groups may be added
-Hydroxyls (or even carbonyls) may be removed
-this increases the complexity of carbohydrate structure
-this is not a PTM because only proteins get translated. But this changes the property of the sugar (ie will
no longer obey the (CH2O)n formula- will now be recognized by different proteins
,isomers - ANSWER-same molecular formula, different structure (ie fructose and glucose)
constitutional isomers - ANSWER-different order of functional group binding. same molecular formula
(ie fructose and glucose- different location of carbonyl group)
stereoisomers and types - ANSWER-same formula and order
they could be enatiomers or diastereoisomers
Enatiomers- non superimposable mirror images
Diastereoisomers- not mirror images
types of diasterosiomers - ANSWER-Epimers: different at one chiral carbon
Anomers: differ at a newly formed, chiral carbon in the ring structure (ie beta-D-glucose and alpha-D-
glucose)
how are reducing sugars formed - ANSWER--in solution
-a sugar is a reducing sugar if a hydroxyl group is free and beside the oxygen in a ring to form back into
the linear structure (yield a positive reducing test)
-the sugar must be in linear form so the aldehyde is free
-the aldehyde group becomes oxidized to reduce copper (the hydrogen on the aldehyde gains an
oxygen)
-the copper 2+ gets reduced to copper + to form Cu2O- this will be detected in solution which will allow
us to determine if a sugar is a reducing sugar
-aldehyde becomes a carboxylic acid, the free H picked up an oxygen
-aldehyde= reducing agent, gets oxidized (from a carbonyl group to carboxylic acid group)
-copper= oxidizing agent, gets reduced
, -these sugars could react with anything in the body so it is not good for too many to be found in the
blood
alpha 1,4 glycosidic bond - ANSWER-ie between 2 alpha glucose molecules
alpha is based on where the hydroxyl is found in the ring
-overall a reducing sugar but one of the sugars that form this disaccharide is not a reducing sugar (the
one on the life)
lectin - ANSWER-proteins that bind to sugars
glycosylation - ANSWER--membrane glycoproteins that have sugar chains linked to Asn amino acid (N
linked) or serine/Thr amino acid (O linked)
-amino acids are attacking the anomeric carbon to form the linkage
-form of PTM that takes place in the ER and golgi (mainly in the ER)
-glycosylation on membrane proteins leads to increased diversity and complexity (asymmetry on he
cell's surface and giving cells different properties depending on the sugar that is present)
-protein glycosylation assists in folding and cellular recognition
O glycosidic bond - ANSWER-the Hydroxyl in methanol attacks the carbon that is attached to a hydroxyl
the alpha configuration
-water is released
-where the other hydroxyl in alpha configuration is found there will be a OCH3 attached to the carbon
(the O glycosidic bond)
what are things that can vary in an oligosaccharide - ANSWER-amino acids (either N or O linked)
sugar types (ie Glucose, fructose of manose)
composition
configuration of D or L hydroxyl (either alpha or beta)
linkages to form glycosidic bonds (1,4 or 1,6)
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