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Midterm 2
Lecture 10: Carbohydrates
Questions:
Where are the hydroxyl groups faced with alpha and beta?
Alpha down and beta up
How are two glucose groups joined and what does it form?
Maltose through an alpha 1,4 - glycosidic bond
What are monosaccharides?
Aldehydes or ketones that contain two or more alcohol groups(CH2O)n
How many C are the smallest monosaccharides composed of?
3
What is the difference between ose and ase?
Ose is sugar and ase is enzyme
What are stereoisomers and what are the 2 types?
Atoms connected in the same order but different spatial arrangement -
enantiomers(nonsuperimposable mirror image) and diastereomers(isomers
that aren’t mirror images of each other with multiple chiral centers)
What are the 2 types of diastereomers?
Epimers - differ in configuration in only a single asymmetric center
Anomers - differ at a new asymmetric carbon atom formed on ring closure
What are the 2 most common pentoses and what is different about them?
Ribose and deoxyribose(ribose has OH or that extra O whereas deoxyribose
has an H)
Midterm 2 1
, What are 4 common hexoses and how are they related?
Glucose, Mannose, Galactose, and Fructose
Glucose and mannose are C2 epimers
Glucose and galactose are C4 epimers
Mannose and galactose are C2 and C4 diastereomers
Fructose is a ketose whereas others are aldoses
What is the chemical basis for a ring formation in sugars?
Aldehyde reacts with alc to form hemiacetal
Ketone reacts with alc to form hemiketal
What is a 6C and 5C sugar structure called?
Pyranose or pyran vs furanose or furan
Is the alpha or beta form of glucopyranose more favorable and why?
Beta because in the alpha form the 2 hydroxyl groups are very close to each
other so sterics
What is a Haworth projection?
A way to show the cyclic form of sugars
Is it better to have alpha or beta glucopyranose in the chair conformation and
why?
Beta because the H take up the axial positions and you want bigger groups in
equatorial to reduce sterics(boat causes sterics as well so not favorable)
What is important about the 2 anomeric forms of glucose?
They are in equilibrium with the open chain form, glucose also reacts with
oxidizing agents
What are the sugars called that react with oxidizing agents?
Reducing sugars
What can glucose as a reducing sugar do?
React with Hb, forming glycosylated HbA1c which is fully functional
Midterm 2 2
, What does determining the amount of HbA1c in the blood help with?
Monitoring long term control of blood glucose levels in diabetics
What can monosaccharides act as and what is an example?
Reducing agents - glucose in open chain react with Cu2+ + Cu+ to form Cu2O,
doing it in a Fehling solution can produce Gluconic acid(changes color)
What does the open chain form have that is so reactive?
Free aldehyde
Is fructose a reducing sugar why or why not?
No because it has a ketone instead of an aldehyde so it isn’t reactive
How can monosaccharides be joined to alcohols and amines?
Through glycosidic bonds
What is an O-glycosidic bond and what is the product known as?
A bond formed between anomeric carbon atom and hydroxyl group of another
molecule - product is glycoside
What is an N-glycosidic bond and what is the product known as?
Bond formed between anomeric carbon atom and amine - product is
glycosamine
What can carbohydrates form that is important in glycolysis?
Ester linkages to phosphates
What does an alcohol and acid form?
Ester - alcohol is the sugar and acid is the phosphate group
What are some modifications of monosaccharides and where are they found?
They are often expressed on cell surfaces
Adding a methyl forms fucose
Adding an N acetyl group forms GaINAc and GlcNAc
Adding N acetyl and glycerol forms Sia
Adding phosphate forms glucose - 6 - phosphate
Midterm 2 3
, What are oligosaccharides?
Contain two or more monosaccharides linked by O-glucosidic bonds
What enzymes and substrates are responsible for oligo assembly?
Glycosyltransferases catalyze the formation of the glycosidic bonds while
uridine diphosphate(UDP) is the substrate that attaches first(for glucose
because the enzyme is GLUCOsyltransferases)
What does alpha glucose and beta fructose form?
Table sugar - Sucrose
What does alpha glucose and beta galactose form?
Milk and sugar - Lactose
What are polysaccharides?
Large polymeric oligosaccharides, if all monosaccharides in the
polysaccharide are the same it is called homopolymer
What is glycogen?
Polysaccharide that is the storage from of glucose in animal cells(starch for
plants)
What bonds are most glucose units in glycogen lined by?
Alpha 1,4 glycosidic bonds with branches formed by alpha 1,6 glycosidic
bonds every 10 glucose units
Where is glycogen mostly found?
Muscle(produce more ATP) and liver(turns back to glucose to regulate blood
glucose)
What is the difference between alpha 1,4 and beta 1,4?
Alpha of starch and glycogen formation form compact hollow cylinders
suitable for accessible storage(nutrition) while beta is for cellulose that yields
a straight chain to interact with other cellulose molecules to form strong
fibrils(structural)
Why don’t mammals have cellulose?
They can’t digest it, it is an important source of fiber
Midterm 2 4
Midterm 2
Lecture 10: Carbohydrates
Questions:
Where are the hydroxyl groups faced with alpha and beta?
Alpha down and beta up
How are two glucose groups joined and what does it form?
Maltose through an alpha 1,4 - glycosidic bond
What are monosaccharides?
Aldehydes or ketones that contain two or more alcohol groups(CH2O)n
How many C are the smallest monosaccharides composed of?
3
What is the difference between ose and ase?
Ose is sugar and ase is enzyme
What are stereoisomers and what are the 2 types?
Atoms connected in the same order but different spatial arrangement -
enantiomers(nonsuperimposable mirror image) and diastereomers(isomers
that aren’t mirror images of each other with multiple chiral centers)
What are the 2 types of diastereomers?
Epimers - differ in configuration in only a single asymmetric center
Anomers - differ at a new asymmetric carbon atom formed on ring closure
What are the 2 most common pentoses and what is different about them?
Ribose and deoxyribose(ribose has OH or that extra O whereas deoxyribose
has an H)
Midterm 2 1
, What are 4 common hexoses and how are they related?
Glucose, Mannose, Galactose, and Fructose
Glucose and mannose are C2 epimers
Glucose and galactose are C4 epimers
Mannose and galactose are C2 and C4 diastereomers
Fructose is a ketose whereas others are aldoses
What is the chemical basis for a ring formation in sugars?
Aldehyde reacts with alc to form hemiacetal
Ketone reacts with alc to form hemiketal
What is a 6C and 5C sugar structure called?
Pyranose or pyran vs furanose or furan
Is the alpha or beta form of glucopyranose more favorable and why?
Beta because in the alpha form the 2 hydroxyl groups are very close to each
other so sterics
What is a Haworth projection?
A way to show the cyclic form of sugars
Is it better to have alpha or beta glucopyranose in the chair conformation and
why?
Beta because the H take up the axial positions and you want bigger groups in
equatorial to reduce sterics(boat causes sterics as well so not favorable)
What is important about the 2 anomeric forms of glucose?
They are in equilibrium with the open chain form, glucose also reacts with
oxidizing agents
What are the sugars called that react with oxidizing agents?
Reducing sugars
What can glucose as a reducing sugar do?
React with Hb, forming glycosylated HbA1c which is fully functional
Midterm 2 2
, What does determining the amount of HbA1c in the blood help with?
Monitoring long term control of blood glucose levels in diabetics
What can monosaccharides act as and what is an example?
Reducing agents - glucose in open chain react with Cu2+ + Cu+ to form Cu2O,
doing it in a Fehling solution can produce Gluconic acid(changes color)
What does the open chain form have that is so reactive?
Free aldehyde
Is fructose a reducing sugar why or why not?
No because it has a ketone instead of an aldehyde so it isn’t reactive
How can monosaccharides be joined to alcohols and amines?
Through glycosidic bonds
What is an O-glycosidic bond and what is the product known as?
A bond formed between anomeric carbon atom and hydroxyl group of another
molecule - product is glycoside
What is an N-glycosidic bond and what is the product known as?
Bond formed between anomeric carbon atom and amine - product is
glycosamine
What can carbohydrates form that is important in glycolysis?
Ester linkages to phosphates
What does an alcohol and acid form?
Ester - alcohol is the sugar and acid is the phosphate group
What are some modifications of monosaccharides and where are they found?
They are often expressed on cell surfaces
Adding a methyl forms fucose
Adding an N acetyl group forms GaINAc and GlcNAc
Adding N acetyl and glycerol forms Sia
Adding phosphate forms glucose - 6 - phosphate
Midterm 2 3
, What are oligosaccharides?
Contain two or more monosaccharides linked by O-glucosidic bonds
What enzymes and substrates are responsible for oligo assembly?
Glycosyltransferases catalyze the formation of the glycosidic bonds while
uridine diphosphate(UDP) is the substrate that attaches first(for glucose
because the enzyme is GLUCOsyltransferases)
What does alpha glucose and beta fructose form?
Table sugar - Sucrose
What does alpha glucose and beta galactose form?
Milk and sugar - Lactose
What are polysaccharides?
Large polymeric oligosaccharides, if all monosaccharides in the
polysaccharide are the same it is called homopolymer
What is glycogen?
Polysaccharide that is the storage from of glucose in animal cells(starch for
plants)
What bonds are most glucose units in glycogen lined by?
Alpha 1,4 glycosidic bonds with branches formed by alpha 1,6 glycosidic
bonds every 10 glucose units
Where is glycogen mostly found?
Muscle(produce more ATP) and liver(turns back to glucose to regulate blood
glucose)
What is the difference between alpha 1,4 and beta 1,4?
Alpha of starch and glycogen formation form compact hollow cylinders
suitable for accessible storage(nutrition) while beta is for cellulose that yields
a straight chain to interact with other cellulose molecules to form strong
fibrils(structural)
Why don’t mammals have cellulose?
They can’t digest it, it is an important source of fiber
Midterm 2 4
