Carbohydrates Flashcards
1
Q
what are the two simplest monosaccharides?
A
- glyceraldehyde (an aldostriose)
- dihydroxyacetone (a ketotriose)
2
Q
what is the classification of monosaccharides based on?
A
number of carbons:
- triose (3)
- tetrose (4)
- pentose (5)
- hexose (6)
- heptose (7)
3
Q
of the triose monosaccharides, which are aldoses and which are ketoses?
A
- aldoses: glycerose/glyceraldehyde
- ketoses: dihydroxyacetone
4
Q
of the tetrose monosaccharides, which are aldoses and which are ketoses?
A
- aldoses: erythrose
- ketoses: erythrulose
5
Q
of the pentose monosaccharides, which are aldoses and which are ketoses?
A
- aldoses: ribose, xylose, arabinose
- ketoses: ribulose, xylulose
6
Q
of the hexose monosaccharides, which are aldoses and which are ketoses?
A
- aldoses: glucose, galactose, mannose
- ketoses: fructose
7
Q
of the heptose monosaccharides, which are aldoses and which are ketoses?
A
- aldoses: glucoheptose, galactoheptose
- ketoses: pseudoheptulose
8
Q
what is an isomer?
A
same molecular formula but different structures
9
Q
what are constitutional isomers?
A
differ in the order of attachment of atoms
10
Q
what are stereoisomers?
A
- atoms are connected in the same order but differ in spatial arrantment
- can be enantiomers or diastereoisomers
11
Q
what are enantiomers?
A
a type of stereoisomer that has a nonsuperimposable mirror image
12
Q
what are diastereoisomers?
A
a type of stereoisomer that are not mirror images
13
Q
what are epimers?
A
a type of diastereoisomer that differs at one of several asymmetric carbon atoms
14
Q
what are anomers?
A
a type of diastereoisomer that differs at a new asymmetric carbon formed on ring closure
15
Q
what is this?
A
D-glucose, monosaccharide, an aldohexose
16
Q
what is this?
A
D-fructose, monosaccharide, a ketohexose
17
Q
are most CHOs in the D or L form?
A
D form
18
Q
what are D-ribose and 2-deoxy-D-ribose?
A
- monosaccharides
- aldopentoses
19
Q
name 3 projection models of molecules
A
- ball and stick models
- fischer projections
- haworth projections
20
Q
name a D-aldotriose
A
- D-glyceraldehyde
- it is a monosaccharide
21
Q
name a D-aldotetrose
A
- D-erythrose
- it is a monosaccharide
22
Q
name three D-aldopentoses
A
-D-ribose -
D-arabinose
-D-xylose
-these are monosaccharides
23
Q
name three D-aldohexoses
A
- D-glucose
- D-mannose
- D-galactose
- these are monosaccharides
24
Q
what is this?
A
- D-galactose
- monosaccharide
- D-aldohexose
25
name a D-ketotriose
- dihydroxyacetone
- this is a monosaccharide
26
name a D-ketotetrose
- D-erythrulose
- this is a monosaccharide
27
name two D-ketopentoses
- D-ribulose
- D-xylulose
28
name a D-ketohexose
-D-fructose
29
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
30
what forms a hemiacetal and acetal?
aldehyde and alcohol forms a hemiacetal, and adding a second alcohol forms an acetal
31
what forms a hemiketal and ketal?
ketone and alcohol forms a hemiketal, and adding a second alcohol forms a ketal
32
does glucose form a hemiacetal or hemiketal?
hemiacetal
33
does fructose form a hemiacetal or hemiketal?
hemiketal
34
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
35
describe furanose and pyranose formation from D-fructose
- a 5-membered ring forms furanose
- a 6-membered ring forms pyranose
36
D-glucopyranose forms chair and boat conformations. Which is more stable?
- chair conformation is more stable
- it is also more common
37
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
38
what two monosaccharides form maltose?
- glucose
- maltose is made via condensation, and it is broken down via hydrolysis
39
what two monosaccharides form sucrose?
glucose and fructose
40
what two monosaccharides form lactose?
glucose and galactose
41
what two monosaccharides for trehalose?
- glucose and glucose
- it is not a reducing sugar because both anomeric carbons are compromised (no OH group attached)
42
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
43
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
44
describe the structure of glycogen
-for every 10 residues of alpha 1-4 linkages, there will be an alpha 1-6 linkage
45
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
46
what is chitin?
it is a structural carbohydrate containing N-acetyl glucosamine units in beta 1-4 linkages
47
what is the function of glycogen?
it is a storage CHO
48
describe N- and O-glycosylation
- forms heteropolysaccharides
- monomers in O-glycosylation are linked to oxygen
- monomers in N-glycosylation are linked to nitrogen
49
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
50
how do glycoproteins and proteoglycans differ in their categorization?
glycoproteins
* N-linked or O-linked
proteoglycans
* based on the nature of their GAG chains
51
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
52
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
53
what are 3 glycoconjugates and where are they found?
- proteoglycans, glycoproteins, and glycolipids
- they are found in the plasma membrane
54
name 4 glycosaminoglycans
1. hyaluronate
2. chondroitin 4-sulfate
3. keratan sulfate
4. heparin - injectable anticoagulant (important in dentistry)
55
what are some characteristics of glycosaminoglycans?
- large polysaccharides with amines
- high molecular weights
- negatively charged
- unusual structures
56
describe how CHOs are informational molecules
the span the plasma membrane and can present things such as antigens, receptors, toxins, viruses, and bacteria
57
what CHO is found in saliva?
mucins
58
what is this?
* glyceraldehyde
* aldotriose
* monosaccharide
59
what is this?
* dihydroxyacetone
* ketotriose
* monosaccharide
60
what is this?
* D-ribose
* aldopentose
* monosaccharide
61
what is this?
* D-erythrose
* aldotetrose
* monosaccharide
62
what is this?
* D-erythrulose
* ketotetrose
* monosaccharide
63
what is this?
* D-ribulose
* ketopentose
* monosaccharide
64
what is this?
* maltose
* glucose + glucose; condensation rxn
* disaccharide
65
what is this?
* lactose
* glucose + galactose
* disaccharide
66
what is this?
* sucrose
* glucose + fructose
* disaccharide
67
stereochemistry:
glyceraldehyde and dihydroxyacetone are \_\_\_\_.
constitutional isomers
68
stereochemistry:
D-glyceraldehyde and L-glyceraldehyde are \_\_\_\_, which is a type of \_\_\_\_.
enantiomers; stereoisomer
69
stereochemistry:
D-altrose and D-glucose are \_\_\_\_, which is a type of \_\_\_\_.
diastereoisomers, stereoisomer
70
stereochemistry:
alpha- and beta-glucose are \_\_\_\_, a type of \_\_\_\_.
anomers; diastereoisomer
71
stereochemistry:
D-glucose and D-mannose are \_\_\_\_, which are types of \_\_\_\_.
epimers, diastereoisomers
72
T or F:
D and L isomers of a sugar are enantiomers
true
73
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
74
what is the only disaccharide that is not a reducing sugar?
sucrose
