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Biochemistry > Chapter 9: Carbohydrates > Flashcards

Chapter 9: Carbohydrates Flashcards

1
Q

what are the other two names for carbohydrates?

A

sugar

saccharide

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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

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3
Q

why are carbohydrates so named?

A

they have the general chemical structure (C*H2O)n

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4
Q

what is a monosaccharide?

A

a single monomer unit of sugar

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5
Q

what is a oligosaccharide?

A

a small polymer of monosaccharides

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6
Q

what is a polysaccharide?

A

a large polymer of monosaccharides groups linked together

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7
Q

what is a glycoprotein?

A

oligosaccharides linked to protein

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8
Q

what is a glycolipid?

A

oligosaccharides linked to lipids

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9
Q

draw the line structure for glucose

A

…

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10
Q

which form of sugar is the biologically relevant form: linear or ring?

A

ring

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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

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12
Q

Which carbohydrate is L carbohydrate?

A

the one whose second to last alcohol is pointing to the left

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13
Q

Which carbohydrate is D carbohydrate?

A

the one whose second to last alcohol is pointing to the right

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14
Q

which form of sugar is the biologically relevant form: L or D?

A

d

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15
Q

What kind of carbonyl does a ketose carbohydrate have?

A

ketone

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16
Q

What kind of carbonyl does a aldose carbohydrate have?

A

aldehyde

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17
Q

Are carbohydrates optically active and chiral?

A

yea

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18
Q

In Fischer projection, which lines are dashed?

A

the vertical ones

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19
Q

In Fischer projection, which lines are wedged?

A

the horizontal ones

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20
Q

which sugar did Dr. Shimko describe as being the foundation for all other sugars?

A

D-Glyceraldehyde

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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

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22
Q

what is the second to last carbon in a carbohydrate called?

A

Penultimate carbon

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23
Q

is ‘glucose’ a common name or a systematic name?

A

common

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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

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25
Q

Which carbohydrate is primarily found in nature as L even though carbohydrates are more often found in nature as D?

A

L-arabinose

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26
Q

what is L-arabinose involved in?

A

photosynthesis

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27
Q

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?

A

all the chiral centers

it’s like a complete mirror image

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28
Q

what 4 prefixes do you need to know to identify the number of carbons in a carbohydrate?

A

triose
tetrose
pentose
hexose

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29
Q

what is D-Glyceraldehyde involved in?

A

glycolysis

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30
Q

What are D-Erythrose and D-Xylose involved in?

A

pentose phosphate pathway

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31
Q

what is D-Ribose involved with?

A

its building block for RNA and DNA

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32
Q

what is D-Glucose involved in?

A

it gets broken down directly by glycolysis

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33
Q

What (biological process) are D-Mannose and D-Galactose involved in?

A

they get broken down in the glycidic cycle?????

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34
Q

What are epimers?

A

molecules that are identical except for rotation around one asymmetric carbon

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35
Q

on which carbon is a carbohydrate’s ketone located?

A

C2

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36
Q

what are Dihydroxyacetone and D-Fructose involved in?

A

glycolysis

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37
Q

what are D-Erythrulose, D-Erythrulose, and D-Xylulose involved in?

A

pentose phosphate pathway

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38
Q

what is the 2nd most important sugar after glucose?

A

D-Fructose

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39
Q

is furanose a 5 membered ring or a 6 membered ring?

A

5

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40
Q

is pyranose a 5 membered ring or a 6 membered ring?

A

6

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41
Q

are ringed carbohydrates aromatic?

A

no

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42
Q

what is a hemiacetal?

A

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

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43
Q

which carbon is the anomeric carbon in a ringed carbohydrate?

A

the one that adopted a new stereocenter during the formation of the hemiacetal

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44
Q

what is an intermolecular hemiacetal?

A

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

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45
Q

what’s a Haworth projection?

A

a simplified method of drawing ring structures with the plane of the ring perpendicular to the page

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46
Q

what is the limitation of Haworth projections?

A

they are not geometrically precise

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47
Q

What is an anomer?

A

A pair of stereoisomers that differ only in

conformation around the anomeric carbon (the carbonyl carbon in the linear form)

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48
Q

what is an α-anomer?

A

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)

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49
Q

what is a β-anomer:

A

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

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50
Q

what is mutarotation?

A

is the process of interconverting between α and β
anomers THROUGH THE LINEAR INTERMEDIATE to reach equilibrium

note the spelling: mutant rotation

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51
Q

What has to be true about a sugar’s anomeric carbon in order for mutarotation to occur?

A

the anomeric carbon must have an alcohol as a substituent

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52
Q

what does it mean to say that a sugar is a reducing sugar?

A

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)

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53
Q

what do you call a reducing sugar that has been oxidized?

A

modified sugar

54
Q

Do both ends of a reducing sugar able to be reducing agents?

A

no

One end is reducing and the other end is non reducing

55
Q

Do we refer to sugars as ‘reducing’ when they’re in their ring form?

A

No

It the reudcy-ness only applies to the linear form, as it still has it’s carbonyl

56
Q

how is directionality established in reducing sugars?

A

we read the sugar from the NON reducing end to the reducing end

57
Q

what does it mean to say that a metal gets reduced by a reducing sugar?

A

the metal receives electrons from the sugar

the sugar gives electrons to the metal

58
Q

Why/how are monosaccharide derivatives examples of modified sugars?

A

yes

59
Q

Are dehydroxy sugars and phosphorylated sugars examples of monosaccharide derivatives/modified sugars?

A

yes

60
Q

which sugars can be reducing sugars?

A

any sugar that can get into its linear form

61
Q

what is the difference between regular glucose and the modified glucose ‘glucosamine’?

A

glucosamine has NH2 group on the C2

62
Q

what is the difference between regular glucose and the modified glucose ‘GlcNaC’?

A

GlcNaC has an acetylene group on its C2 that turns glycosidic bond into an amide linkage

63
Q

what is the difference between regular glucose and the modified glucose ‘GlcNaC’?

A

GlcNaC has an acetylene group on its C2 that turns glycosidic bond into an amide linkage

64
Q

what is a glycosidic bond?

A

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
Q

what is the difference between regular glucose and the modified glucose ‘GalNaC’?

A

GalNaC has an amine at the C2 position

66
Q

what is GalNaC actually called?

A

N-acetylgalactosamine

67
Q

what is GlcNaC actually called?

A

N-Acetylglucosamine

68
Q

what is chitin for?

A

exoskeleton

69
Q

can a sugar engage in mutarotation after it’s reacted its anomeric carbon to make a glycosidic bond?

A

no. The new glycosidic bond is so stable that the anomers can no longer interconvert by mutarotation

70
Q

why can’t sugars do mutarotation anymore after they’ve made glycosidic bonds?

A

it would require breaking a carbon-oxygen bonds, which is highly unlikely to occur without intervention from an agent like a glycosidase enzyme

71
Q

what does a glycosidase enzyme do?

A

enzymes that selectively cleave glycosidic bonds

72
Q

why can’t sugars do mutarotation anymore after they’ve made glycosidic bonds?

A

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
Q

can alpha and beta glycocidic bonds be broken with the same glycosidases?

A

no

alpha glycocidic bonds require alpha glycosidase
beta glycocidic bonds require beta glycosidase

74
Q

can alpha and beta glycocidic bonds be broken with the same glycosidases?

A

no

alpha glycocidic bonds require alpha glycosidase
beta glycocidic bonds require beta glycosidase

75
Q

Do humans make both alpha glycosidase

and beta glycosidase?

A

No.

We primarily make alpha (which is why we can’t break down disaccharide sugars that are beta)

76
Q

Do humans make both alpha glycosidase

and beta glycosidase ?

A

No.

As adults, we primarily make alpha (which is why we can’t break down milk fat)

77
Q

What is an N-glycosidic bond?

A

a glycocidic bond linked through a nitrogen

78
Q

what mechanism do sugars to do generate glycocidic bonds with one another?

A

condensation

79
Q

what mechanism is the reverse of the one sugars to do generate glycocidic bonds with one another?

A

hydrolysis

80
Q

what is maltose?

A

what you get when you bind 2 glucoses together

81
Q

Does stereochemistry define common glucose disaccharides (like maltose and cellobiose)?

A

yes

slides p 14

82
Q

Are there multiple types of glucose-glucose disaccharides ?

A

yes

83
Q

what is maltose the disaccharide unit for?

A

it’s the disaccharide unit of starch (α-linkage)

84
Q

what is starch?

A

Starch is a polysaccharide formed by units of glucose and the storage form of carbohydrates in plants.

85
Q

what is cellobiose the disaccharide unit for?

A

Cellobiose is the disaccharide unit of cellulose (β-linkage

86
Q

what is cellulose?

A

an insoluble substance which is the main constituent of plant cell walls and of vegetable fibers such as cotton.

87
Q

what does it mean to say you have a 1-4 glycidic bond?

A

it means the anomeric carbon from one sugar (C1) is bound to the C4 carbon of the other sugar

88
Q

what is the difference between a 1-4 linked maltose and a 1-4 linked cellobiose?

A

in the maltose, the anomeric carbon (C1) is alpha.

in the cellobiose, the anomeric carbon (C1) is beta

89
Q

can the reducing end of a maltose or cellobiose do mutarotation?

A

yes. As long as they still have their alcohol substituents on their anomeric carbons, they can still do mutarotation

90
Q

Can humans break maltose and cellobiose into their monomers in order to free the glucose and use it for energy production?

A

We make the alpha glycosidase enzyme needed to break maltose but not the beta glycosidase enzyme to break cellobiose

91
Q

how does the body use broken down maltose?

A

we absorb into the intestinal cells and transfer to the blood stream to be moved around the body for energy production

92
Q

what is the sucrose (table sugar) disaccharide composed of?

A

a glucose and a fructose with an alpha 1- beta 2 glycosidic linkage

93
Q

Why doesn’t the disaccharide ‘sucrose’ have any reducing ends?

A

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
Q

is sucrose a reducing sugar or non reducing sugar?

A

non reducing

95
Q

what enzyme do humans use to break down sucrose into its constituent pieces (glucose & fructose)?

A

sucrase enzyme

96
Q

what is another name for lactose?

A

milk sugar

97
Q

what is the lactose disaccharide composed of?

A

a galactose sugar with a beta 1-4 linkage to glucose

98
Q

which part of the lactose is the NON reducing end?

A

the galactose end

99
Q

Is lactose the only disaccharide with beta linkage that adult humans can digest?

A

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
Q

what mechanism does glycosidase use?

A

hydrolysis

101
Q

what is the difference between exoglycosidase enzymes and ENDOglycosidase enzymes?

A

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
Q

are digestive enzymes examples of exoglycosidase enzymes or ENDOglycosidase enzymes?

A

endo

103
Q

what is the type, repeating unit, and linkage for amylose?

A

type: homopolysaccharide

repeating unit/linkage: alpha 1-4 glucose; linear/no branches

104
Q

what is amylose polysaccharide found in?

A

energy storage

105
Q

what is amylose polysaccharide used for?

A

energy storage in plants

106
Q

does amylose have a threadlike structure or a spiral like structure?

A

spiral

107
Q

why is the release of energy from amylose slow?

A

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
Q

what is the type, repeating unit, and linkage for amylopectin?

A

type: homopolysaccharide

repeating unit/linkage: alpha 1-4 glucose in the main chain, alpha 1-6 glucose in the branched chains

109
Q

How frequent are the branches in amylopectin?

A

About every 24-30 sugar residues

110
Q

How is amylopectin r/t amylose?

A

Amylopectin is derived from amylose and is very similar except that it has branches and amylose does not.

111
Q

what is amylopectin polysaccharide used for?

A

energy storage in plants

112
Q

why is the release of energy from amylopectin relatively fast?

A

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
Q

what two polysaccharides together comprise starch?

A

amylose and amylopectin

114
Q

what is the type, repeating unit, and linkage for glycogen?

A

type: homopolysaccharide

repeating unit/linkage: alpha 1-4 glucose in the main chain, alpha 1-6 glucose in the branched chains

115
Q

How frequent are the branches in glycogen?

A

About every 8-12 sugar residues

116
Q

what is glycogen polysaccharide used for?

A

energy storage in bacteria and animal cells

primary storage for excess glucose

117
Q

of the 5 polysaccharides you have to memorize, which 2 have branches?

A

amylose and glycogen

118
Q

what small peptide makes glycogen?

A

glycogenin

119
Q

what is the cleaving enzyme for glycogen?

A

glycogen phosphorylase

120
Q

why is the cleaving enzyme for glycogen (glycogen phosphorylase ) so named?

A

it cleaves by phosphorolysis instead of hydrolysis

121
Q

what is phosphorolysis?

A

is the cleavage of a compound in which inorganic phosphate is the attacking group

similar to hydrolysis

122
Q

why is the release of energy from glycogen relatively fast?

A

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
Q

what is the type, repeating unit, and linkage for cellulose?

A

type: homopolysaccharide

repeating unit/linkage: beta 1-4 glucose in the main chain

124
Q

does cellulose have a threadlike structure or a spiral like structure?

A

threadlike

125
Q

what is the cleaving enzyme for cellulose?

A

May be broken up by cellulases: enzymes secreted by

some fungi, bacteria, and protozoa

126
Q

why is cellulose useful as a structural material for plant cell walls?

A

Its thread orient themselves in an intricate repeating pattern is rigid and fibrous

127
Q

what is the type, repeating unit, and linkage for chitin?

A

Type: homopolysaccharide

repeating unit/linkage: beta 1-4 GlcNAc in the main chain

128
Q

what is chitin found in?

A

fungal cell walls and arthropod exoskeleton

129
Q

why is chitin so useful as a structural sugar?

A

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
Q

what gives amylose a spiral shape (instead of a threadlike shape)

A

the stereochemistry of its anomeric carbons

131
Q

what are the two main reasons that forming sugar polymers from monomers is favorable?

A

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

Biochemistry (23 decks)

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