Chapter 9: Carbohydrates Flashcards
1
Q
what are the other two names for carbohydrates?
A
sugar
saccharide
2
Q
what is a carbohydrate?
A
aldehyde or ketone compounds where every carbon in the structure is an alcohol except for one: the carbonyl
3
Q
why are carbohydrates so named?
A
they have the general chemical structure (C*H2O)n
4
Q
what is a monosaccharide?
A
a single monomer unit of sugar
5
Q
what is a oligosaccharide?
A
a small polymer of monosaccharides
6
Q
what is a polysaccharide?
A
a large polymer of monosaccharides groups linked together
7
Q
what is a glycoprotein?
A
oligosaccharides linked to protein
8
Q
what is a glycolipid?
A
oligosaccharides linked to lipids
9
Q
draw the line structure for glucose
A
…
10
Q
which form of sugar is the biologically relevant form: linear or ring?
A
ring
11
Q
How do you know whether a carbohydrate is a D or and L carbohydrate?
A
you look at which way the second to last alcohol is pointed
12
Q
Which carbohydrate is L carbohydrate?
A
the one whose second to last alcohol is pointing to the left
13
Q
Which carbohydrate is D carbohydrate?
A
the one whose second to last alcohol is pointing to the right
14
Q
which form of sugar is the biologically relevant form: L or D?
A
d
15
Q
What kind of carbonyl does a ketose carbohydrate have?
A
ketone
16
Q
What kind of carbonyl does a aldose carbohydrate have?
A
aldehyde
17
Q
Are carbohydrates optically active and chiral?
A
yea
18
Q
In Fischer projection, which lines are dashed?
A
the vertical ones
19
Q
In Fischer projection, which lines are wedged?
A
the horizontal ones
20
Q
which sugar did Dr. Shimko describe as being the foundation for all other sugars?
A
D-Glyceraldehyde
21
Q
Why did Dr. Shimko describe D-Glyceraldehyde as being the foundation for all other sugars?
A
because it is the bases for how we assign stereochemistry to all carbohydrates
22
Q
what is the second to last carbon in a carbohydrate called?
A
Penultimate carbon
23
Q
is ‘glucose’ a common name or a systematic name?
A
common
24
Q
why do biochemists use the penultimate carbon to determine carbohydrate stereochemistry instead of the R S system?
A
So that they don’t have to determine the R and S for every single chiral center
25
Which carbohydrate is primarily found in nature as L even though carbohydrates are more often found in nature as D?
L-arabinose
26
what is L-arabinose involved in?
photosynthesis
27
when you draw the D version of an L carbohydrate (or vice versa) do you have to reverse all the chiral centers or just the penultimate chiral center?
all the chiral centers
it's like a complete mirror image
28
what 4 prefixes do you need to know to identify the number of carbons in a carbohydrate?
triose
tetrose
pentose
hexose
29
what is D-Glyceraldehyde involved in?
glycolysis
30
What are D-Erythrose and D-Xylose involved in?
pentose phosphate pathway
31
what is D-Ribose involved with?
its building block for RNA and DNA
32
what is D-Glucose involved in?
it gets broken down directly by glycolysis
33
What (biological process) are D-Mannose and D-Galactose involved in?
they get broken down in the glycidic cycle?????
34
What are epimers?
molecules that are identical except for rotation around one asymmetric carbon
35
on which carbon is a carbohydrate's ketone located?
C2
36
what are Dihydroxyacetone and D-Fructose involved in?
glycolysis
37
what are D-Erythrulose, D-Erythrulose, and D-Xylulose involved in?
pentose phosphate pathway
38
what is the 2nd most important sugar after glucose?
D-Fructose
39
is furanose a 5 membered ring or a 6 membered ring?
5
40
is pyranose a 5 membered ring or a 6 membered ring?
6
41
are ringed carbohydrates aromatic?
no
42
what is a hemiacetal?
what you call it when a sugar converts from its linear form to a ring structure by nucleophilic attack of the carbonyl by an alcohol
43
which carbon is the anomeric carbon in a ringed carbohydrate?
the one that adopted a new stereocenter during the formation of the hemiacetal
44
what is an intermolecular hemiacetal?
what you call it when a sugar converts from its linear form to a ring structure by nucleophilic attack of its carbonyl by one of its alcohols
45
what's a Haworth projection?
a simplified method of drawing ring structures with the plane of the ring perpendicular to the page
46
what is the limitation of Haworth projections?
they are not geometrically precise
47
What is an anomer?
A pair of stereoisomers that differ only in
| conformation around the anomeric carbon (the carbonyl carbon in the linear form)
48
what is an α-anomer?
what you call it when the OH substituent of the anomeric carbon is on the opposite face of the ring from the CH2OH group which helps to define D/L-stereochemistry
alphas are down right dirty (OH points down in the ring and right on the line structure)
49
what is a β-anomer:
what you call it when the OH substituent of the anomeric carbon is on the same face of the ring as the CH2OH group that helps to define D/L-stereochemistry
(betas point up in the ring and left in the line structure)
I imagine Anne and MC Hammer standing on the same plane of a ring, but in secret...on the down low
50
what is mutarotation?
is the process of interconverting between α and β
anomers THROUGH THE LINEAR INTERMEDIATE to reach equilibrium
note the spelling: mutant rotation
51
What has to be true about a sugar's anomeric carbon in order for mutarotation to occur?
the anomeric carbon must have an alcohol as a substituent
52
what does it mean to say that a sugar is a reducing sugar?
Sugars that have not formed a bond through their anomeric carbon (read: linear sugars) may act as a reducing agents and may be referred to as reducing sugars
sugars that can act as reducing agents because their anomeric carbon is, having it's carbonyl (C=O bond) in tact, can be oxidized (by metals)
53
what do you call a reducing sugar that has been oxidized?
modified sugar
54
Do both ends of a reducing sugar able to be reducing agents?
no
One end is reducing and the other end is non reducing
55
Do we refer to sugars as 'reducing' when they're in their ring form?
No
It the reudcy-ness only applies to the linear form, as it still has it's carbonyl
56
how is directionality established in reducing sugars?
we read the sugar from the NON reducing end to the reducing end
57
what does it mean to say that a metal gets reduced by a reducing sugar?
the metal receives electrons from the sugar
the sugar gives electrons to the metal
58
Why/how are monosaccharide derivatives examples of modified sugars?
yes
59
Are dehydroxy sugars and phosphorylated sugars examples of monosaccharide derivatives/modified sugars?
yes
60
which sugars can be reducing sugars?
any sugar that can get into its linear form
61
what is the difference between regular glucose and the modified glucose 'glucosamine'?
glucosamine has NH2 group on the C2
62
what is the difference between regular glucose and the modified glucose 'GlcNaC'?
GlcNaC has an acetylene group on its C2 that turns glycosidic bond into an amide linkage
63
what is the difference between regular glucose and the modified glucose 'GlcNaC'?
GlcNaC has an acetylene group on its C2 that turns glycosidic bond into an amide linkage
64
what is a glycosidic bond?
what you call it with you link sugars together with covalent bonds through their anomeric carbon
(like how peptide bonds/amide bonds exist between amino acids)
65
what is the difference between regular glucose and the modified glucose 'GalNaC'?
GalNaC has an amine at the C2 position
66
what is GalNaC actually called?
N-acetylgalactosamine
67
what is GlcNaC actually called?
N-Acetylglucosamine
68
what is chitin for?
exoskeleton
69
can a sugar engage in mutarotation after it's reacted its anomeric carbon to make a glycosidic bond?
no. The new glycosidic bond is so stable that the anomers can no longer interconvert by mutarotation
70
why can't sugars do mutarotation anymore after they've made glycosidic bonds?
it would require breaking a carbon-oxygen bonds, which is highly unlikely to occur without intervention from an agent like a glycosidase enzyme
71
what does a glycosidase enzyme do?
enzymes that selectively cleave glycosidic bonds
72
why can't sugars do mutarotation anymore after they've made glycosidic bonds?
it would require breaking a carbon-oxygen bond
| (ether linkage), which is highly unlikely to occur without intervention from an agent like a glycosidase enzyme
73
can alpha and beta glycocidic bonds be broken with the same glycosidases?
no
alpha glycocidic bonds require alpha glycosidase
beta glycocidic bonds require beta glycosidase
74
can alpha and beta glycocidic bonds be broken with the same glycosidases?
no
alpha glycocidic bonds require alpha glycosidase
beta glycocidic bonds require beta glycosidase
75
Do humans make both alpha glycosidase
| and beta glycosidase?
No.
We primarily make alpha (which is why we can't break down disaccharide sugars that are beta)
76
Do humans make both alpha glycosidase
| and beta glycosidase ?
No.
As adults, we primarily make alpha (which is why we can't break down milk fat)
77
What is an N-glycosidic bond?
a glycocidic bond linked through a nitrogen
78
what mechanism do sugars to do generate glycocidic bonds with one another?
condensation
79
what mechanism is the reverse of the one sugars to do generate glycocidic bonds with one another?
hydrolysis
80
what is maltose?
what you get when you bind 2 glucoses together
81
Does stereochemistry define common glucose disaccharides (like maltose and cellobiose)?
yes
slides p 14
82
Are there multiple types of glucose-glucose disaccharides ?
yes
83
what is maltose the disaccharide unit for?
it's the disaccharide unit of starch (α-linkage)
84
what is starch?
Starch is a polysaccharide formed by units of glucose and the storage form of carbohydrates in plants.
85
what is cellobiose the disaccharide unit for?
Cellobiose is the disaccharide unit of cellulose (β-linkage
86
what is cellulose?
an insoluble substance which is the main constituent of plant cell walls and of vegetable fibers such as cotton.
87
what does it mean to say you have a 1-4 glycidic bond?
it means the anomeric carbon from one sugar (C1) is bound to the C4 carbon of the other sugar
88
what is the difference between a 1-4 linked maltose and a 1-4 linked cellobiose?
in the maltose, the anomeric carbon (C1) is alpha.
in the cellobiose, the anomeric carbon (C1) is beta
89
can the reducing end of a maltose or cellobiose do mutarotation?
yes. As long as they still have their alcohol substituents on their anomeric carbons, they can still do mutarotation
90
Can humans break maltose and cellobiose into their monomers in order to free the glucose and use it for energy production?
We make the alpha glycosidase enzyme needed to break maltose but not the beta glycosidase enzyme to break cellobiose
91
how does the body use broken down maltose?
we absorb into the intestinal cells and transfer to the blood stream to be moved around the body for energy production
92
what is the sucrose (table sugar) disaccharide composed of?
a glucose and a fructose with an alpha 1- beta 2 glycosidic linkage
93
Why doesn't the disaccharide 'sucrose' have any reducing ends?
because both anomeric carbons are tied up in the glycosidic bond; neither of them have the OH substituent needed to allow them to engage in mutarotation
94
is sucrose a reducing sugar or non reducing sugar?
non reducing
95
what enzyme do humans use to break down sucrose into its constituent pieces (glucose & fructose)?
sucrase enzyme
96
what is another name for lactose?
milk sugar
97
what is the lactose disaccharide composed of?
a galactose sugar with a beta 1-4 linkage to glucose
98
which part of the lactose is the NON reducing end?
the galactose end
99
Is lactose the only disaccharide with beta linkage that adult humans can digest?
yes children make beta galactosidase enzyme that breaks the linkage in the lactose
some adults' beta galactosidase is non-functional but their gut bacteria can break down the lactase (but the bacteria make gas in the process).
100
what mechanism does glycosidase use?
hydrolysis
101
what is the difference between exoglycosidase enzymes and ENDOglycosidase enzymes?
exoglycosidases bind to a sugar at the non-reducing and and cleave sugar monomers off of the chain one at a time as they make their way towards the reducing end of the sugar chain.
ENDOglycosidase can bind to a sugar chain anywhere (such as in the middle of the sugar chain)
102
are digestive enzymes examples of exoglycosidase enzymes or ENDOglycosidase enzymes?
endo
103
what is the type, repeating unit, and linkage for amylose?
type: homopolysaccharide
repeating unit/linkage: alpha 1-4 glucose; linear/no branches
104
what is amylose polysaccharide found in?
energy storage
105
what is amylose polysaccharide used for?
energy storage in plants
106
does amylose have a threadlike structure or a spiral like structure?
spiral
107
why is the release of energy from amylose slow?
amylose does NOT have branches and thus does not have many non-reducing ends for glycosidase enzymes to bind to and perform hydrolysis (cleavage of sugar monomers at the glycosidic linkages) for the purposes of releasing energy.
108
what is the type, repeating unit, and linkage for amylopectin?
type: homopolysaccharide
repeating unit/linkage: alpha 1-4 glucose in the main chain, alpha 1-6 glucose in the branched chains
109
How frequent are the branches in amylopectin?
About every 24-30 sugar residues
110
How is amylopectin r/t amylose?
Amylopectin is derived from amylose and is very similar except that it has branches and amylose does not.
111
what is amylopectin polysaccharide used for?
energy storage in plants
112
why is the release of energy from amylopectin relatively fast?
amylopectin has many branches and thus has many non-reducing ends for glycosidase enzymes to bind to and perform hydrolysis (cleavage of sugar monomers at the glycosidic linkages) for the purposes of releasing energy.
113
what two polysaccharides together comprise starch?
amylose and amylopectin
114
what is the type, repeating unit, and linkage for glycogen?
type: homopolysaccharide
repeating unit/linkage: alpha 1-4 glucose in the main chain, alpha 1-6 glucose in the branched chains
115
How frequent are the branches in glycogen?
About every 8-12 sugar residues
116
what is glycogen polysaccharide used for?
energy storage in bacteria and animal cells
primary storage for excess glucose
117
of the 5 polysaccharides you have to memorize, which 2 have branches?
amylose and glycogen
118
what small peptide makes glycogen?
glycogenin
119
what is the cleaving enzyme for glycogen?
glycogen phosphorylase
120
why is the cleaving enzyme for glycogen (glycogen phosphorylase ) so named?
it cleaves by phosphorolysis instead of hydrolysis
121
what is phosphorolysis?
is the cleavage of a compound in which inorganic phosphate is the attacking group
similar to hydrolysis
122
why is the release of energy from glycogen relatively fast?
glycogen has many branches and thus has many non-reducing ends for glycosidase enzymes to bind to and perform hydrolysis (cleavage of sugar monomers at the glycosidic linkages) for the purposes of releasing energy.
123
what is the type, repeating unit, and linkage for cellulose?
type: homopolysaccharide
repeating unit/linkage: beta 1-4 glucose in the main chain
124
does cellulose have a threadlike structure or a spiral like structure?
threadlike
125
what is the cleaving enzyme for cellulose?
May be broken up by cellulases: enzymes secreted by
| some fungi, bacteria, and protozoa
126
why is cellulose useful as a structural material for plant cell walls?
Its thread orient themselves in an intricate repeating pattern is rigid and fibrous
127
what is the type, repeating unit, and linkage for chitin?
Type: homopolysaccharide
repeating unit/linkage: beta 1-4 GlcNAc in the main chain
128
what is chitin found in?
fungal cell walls and arthropod exoskeleton
129
why is chitin so useful as a structural sugar?
its sugar monomers pack tightly and orient themselves such that they can engage in hydrogen bonding without the need for water as a solvent. This give the chitin polymer rigidity.
130
what gives amylose a spiral shape (instead of a threadlike shape)
the stereochemistry of its anomeric carbons
131
what are the two main reasons that forming sugar polymers from monomers is favorable?
Polymers reduce the concentration of glucose based molecules (from 0.4 M in the monomer, glucose form
to 0.01 µM in the polymer glycogen form), and thereby:
1. reduces osmotic stress on the cell (because the tightly packed subunits can orient themselves such that they can facilitate H bonding w/o water)
2. makes it easier for the cell to regulate glucose, move it in & out of the cell, and take in/store excess glucose in the form of glycogen the lower concentration
gradient for glucose uptake
