Carbohydrates Flashcards
what are the two simplest monosaccharides?
- glyceraldehyde (an aldostriose)
- dihydroxyacetone (a ketotriose)
what is the classification of monosaccharides based on?
number of carbons:
- triose (3)
- tetrose (4)
- pentose (5)
- hexose (6)
- heptose (7)
of the triose monosaccharides, which are aldoses and which are ketoses?
- aldoses: glycerose/glyceraldehyde
- ketoses: dihydroxyacetone
of the tetrose monosaccharides, which are aldoses and which are ketoses?
- aldoses: erythrose
- ketoses: erythrulose
of the pentose monosaccharides, which are aldoses and which are ketoses?
- aldoses: ribose, xylose, arabinose
- ketoses: ribulose, xylulose
of the hexose monosaccharides, which are aldoses and which are ketoses?
- aldoses: glucose, galactose, mannose
- ketoses: fructose
of the heptose monosaccharides, which are aldoses and which are ketoses?
- aldoses: glucoheptose, galactoheptose
- ketoses: pseudoheptulose
what is an isomer?
same molecular formula but different structures
what are constitutional isomers?
differ in the order of attachment of atoms
what are stereoisomers?
- atoms are connected in the same order but differ in spatial arrantment
- can be enantiomers or diastereoisomers
what are enantiomers?
a type of stereoisomer that has a nonsuperimposable mirror image
what are diastereoisomers?
a type of stereoisomer that are not mirror images
what are epimers?
a type of diastereoisomer that differs at one of several asymmetric carbon atoms
what are anomers?
a type of diastereoisomer that differs at a new asymmetric carbon formed on ring closure
what is this?
D-glucose, monosaccharide, an aldohexose
what is this?
D-fructose, monosaccharide, a ketohexose
are most CHOs in the D or L form?
D form
what are D-ribose and 2-deoxy-D-ribose?
- monosaccharides
- aldopentoses
name 3 projection models of molecules
- ball and stick models
- fischer projections
- haworth projections
name a D-aldotriose
- D-glyceraldehyde
- it is a monosaccharide
name a D-aldotetrose
- D-erythrose
- it is a monosaccharide
name three D-aldopentoses
-D-ribose -
D-arabinose
-D-xylose
-these are monosaccharides
name three D-aldohexoses
- D-glucose
- D-mannose
- D-galactose
- these are monosaccharides
what is this?
- D-galactose
- monosaccharide
- D-aldohexose
name a D-ketotriose
- dihydroxyacetone
- this is a monosaccharide
name a D-ketotetrose
- D-erythrulose
- this is a monosaccharide
name two D-ketopentoses
- D-ribulose
- D-xylulose
name a D-ketohexose
-D-fructose
describe how D-mannose and D-galactose are epimers of D-glucose
- D-mannose is an epimer at C-2
- D-galactose is an epimer at C-4
what forms a hemiacetal and acetal?
aldehyde and alcohol forms a hemiacetal, and adding a second alcohol forms an acetal
what forms a hemiketal and ketal?
ketone and alcohol forms a hemiketal, and adding a second alcohol forms a ketal
does glucose form a hemiacetal or hemiketal?
hemiacetal
does fructose form a hemiacetal or hemiketal?
hemiketal
describe pyranose formation from D-glucose
- the OH group on the 5th carbon reacts with the aldehyde group on the 1st carbon to form a ring
- in the alpha form, the OH group on the 1st carbon points down
- in the beta form, the OH group on the 1st carbon points up
describe furanose and pyranose formation from D-fructose
- a 5-membered ring forms furanose
- a 6-membered ring forms pyranose
D-glucopyranose forms chair and boat conformations. Which is more stable?
- chair conformation is more stable
- it is also more common
what is a reducing sugar?
- all monosaccharides and most disaccharides are reducing sugars
- it is any sugar that is capable of acting as a reducing agent (aka capable of oxidizing) because it has a free aldehyde group or a free ketone group
- reducing sugars can be identified as having anomeric carbons with an OH group
what two monosaccharides form maltose?
- glucose
- maltose is made via condensation, and it is broken down via hydrolysis
what two monosaccharides form sucrose?
glucose and fructose
what two monosaccharides form lactose?
glucose and galactose
what two monosaccharides for trehalose?
- glucose and glucose
- it is not a reducing sugar because both anomeric carbons are compromised (no OH group attached)
what linkage does the polysaccharide cellulose contain, and what is the enzyme needed to break it that humans do not have?
- beta 1-4 linkage
- cellulase
- cellulose is part of the microfibril structure of plant cell walls
describe the structure of starch
amylose is linear and contains alpha 1-4 linkages for the first 50 residues, and then turns into amylopectin which has big branches of alpha 1-6 linkages
describe the structure of glycogen
-for every 10 residues of alpha 1-4 linkages, there will be an alpha 1-6 linkage
what is the difference between homopolysaccharides and heteropolysaccharides?
- homopolysaccharides are composed of 2 or more of the same monomer
- heteropolysaccharides are composed of 2 or more different monomers
what is chitin?
it is a structural carbohydrate containing N-acetyl glucosamine units in beta 1-4 linkages
what is the function of glycogen?
it is a storage CHO
describe N- and O-glycosylation
- forms heteropolysaccharides
- monomers in O-glycosylation are linked to oxygen
- monomers in N-glycosylation are linked to nitrogen
what are the structural differences between glycoproteins and proteoglycans?
glycoproteins:
- protein w/oligosaccharide chain covalently attached to polypeptide side chain
- short, branched CHO chain; may be negatively charged
proteoglycans:
- subclass of glycoproteins
- core protein with 1+ covalently attached GAG chains
- long, linear, negatively charged CHO polymer chains
how do glycoproteins and proteoglycans differ in their categorization?
glycoproteins
- N-linked or O-linked
proteoglycans
- based on the nature of their GAG chains
how do glycoproteins and proteoglycans differ functionally?
glycoproteins
- cell-cell recognition (ex. ABO blood group antigens)
proteoglycans
- modulation of cell growth processes or cushioning in joints
where are glycoproteins and proteoglycans found?
glycoproteins
- found on cell surfaces
- most are integral membrane proteins
proteoglycans
- found mainly in CT
- contribute to the organization and physical propeties of the ECM
what are 3 glycoconjugates and where are they found?
- proteoglycans, glycoproteins, and glycolipids
- they are found in the plasma membrane
name 4 glycosaminoglycans
- hyaluronate
- chondroitin 4-sulfate
- keratan sulfate
- heparin - injectable anticoagulant (important in dentistry)
what are some characteristics of glycosaminoglycans?
- large polysaccharides with amines
- high molecular weights
- negatively charged
- unusual structures
describe how CHOs are informational molecules
the span the plasma membrane and can present things such as antigens, receptors, toxins, viruses, and bacteria
what CHO is found in saliva?
mucins
what is this?
- glyceraldehyde
- aldotriose
- monosaccharide
what is this?
- dihydroxyacetone
- ketotriose
- monosaccharide
what is this?
- D-ribose
- aldopentose
- monosaccharide
what is this?
- D-erythrose
- aldotetrose
- monosaccharide
what is this?
- D-erythrulose
- ketotetrose
- monosaccharide
what is this?
- D-ribulose
- ketopentose
- monosaccharide
what is this?
- maltose
- glucose + glucose; condensation rxn
- disaccharide
what is this?
- lactose
- glucose + galactose
- disaccharide
what is this?
- sucrose
- glucose + fructose
- disaccharide
stereochemistry:
glyceraldehyde and dihydroxyacetone are ____.
constitutional isomers
stereochemistry:
D-glyceraldehyde and L-glyceraldehyde are ____, which is a type of ____.
enantiomers; stereoisomer
stereochemistry:
D-altrose and D-glucose are ____, which is a type of ____.
diastereoisomers, stereoisomer
stereochemistry:
alpha- and beta-glucose are ____, a type of ____.
anomers; diastereoisomer
stereochemistry:
D-glucose and D-mannose are ____, which are types of ____.
epimers, diastereoisomers
T or F:
D and L isomers of a sugar are enantiomers
true
T or F:
the position of the ketone gives ketoses one more assymetric center than their isometric aldoses
false:
it gives ketoses one less assymetric center than their isometric aldoses
what is the only disaccharide that is not a reducing sugar?
sucrose
