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BIOL 2421 - Cellular Biochem > 11. Carbohydrate structure and function > Flashcards

11. Carbohydrate structure and function Flashcards

1
Q

which biological macromolecule is the most abundant

A

carbohydrates

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2
Q

besides cell respiration, list some of the other roles of carbs

A

structural elements of cell walls or animal connective tissues, cell-cell recognition, cell adhesion or signaling, support skeletal joints

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3
Q

how many monomeric units do monosaccharides have

A

1

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4
Q

how many monomeric units do disaccharides have

A

2

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5
Q

how many monomeric units do oligosaccharides have

A

2-20

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6
Q

how many monomeric units do polysaccharides have

A

20+

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7
Q

what are carb polymers sometimes referred to as

A

glycans

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8
Q

what is a glycan

A

a name used to refer to carb polymers

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9
Q

what is a homoglycan

A

identical monomers

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10
Q

what is a heteroglycan

A

different monomers

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11
Q

what are glycoconjugates

A

carbohydrates covalently attached to another molecule (ie non-sugar molecules such as proteins)

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12
Q

what 2 functional groups will a monosaccharide be bonded to

A

aldehydes or ketones

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13
Q

what is the name for a monosaccharide with an aldehyde

A

an aldose

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14
Q

what is the name for a monosaccharide with a ketone

A

a ketose

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15
Q

what shape is the backbone of most common monosaccharides

A

linear chains

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16
Q

in a monosaccharide structure, what are the carbons bound to

A

one will be bound to a double bond (aldose or ketose), and all the other carbons will be bound to OH and H

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17
Q

how do you determine the type of enantiomer a monosaccharide is

A

look at the chiral carbon farthest from the carbonyl carbon, and see which side the OH is on

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18
Q

which side is the OH for the D enantiomer

A

right

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19
Q

which side is the OH for the L enantiomer

A

left

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20
Q

how do you get the name of a 4C or 5C ketose

A

often, you just add “ul” to the name of the corresponding aldose

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21
Q

define epimers

A

two diastereomers that differ only in the configuration at one carbon

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22
Q

how do cyclic structures form for monosaccharides

A

the carbonyl carbon can react with an intramolecular hydroxyl group

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23
Q

what is the resulting structure of a monosaccharide cyclizing

A

the O of the OH is incorporated into the cycle = hemiacteals or hemiketals, and a new chiral center is formed

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24
Q

how many stereoisomers are produced when a monosaccharide cyclizes

A

2

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25
Q

how are the stereoisomers of cyclization denoted

A

alpha and beta (OH pointing up is beta, OH pointing down is alpha)

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26
Q

since the two stereoisomers of cyclization only differ at the hemiacetal/hemiketal carbon, what are they called

A

anomers

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27
Q

what are the 2 names of 5 and 6 membered rings with one oxygen

A

furanoses and pyranoses

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28
Q

what is a furanose

A

a 5 membered ring with an oxygen

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29
Q

what is a pyranose

A

a six membered ring with an oxygen

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30
Q

to convert a cyclic drawing to a linear drawing, which way does a sub going below the plane go on the linear drawing

A 
down = right
left = up
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31
Q

what is mutarotation

A

when the alpha and beta anomers interconvert configurations. It involves breaking bonds and opening up the ring temporarily

32
Q

what is the product of mutarotation (in glucose solution)

A

1/3 alpha-D-glucose
2/3 beta-D-glucose
a teeny bit of linear glucose
a teeny bit of glucofuranose

33
Q

what are the two haworth projections

A

chair or boat

34
Q

T or F: you can turn the planar ring into the chair or boat conformation without breaking any bonds

A

true

35
Q

what are the 4 non-polymerized monosaccharide derivatives

A

sugar phosphates, deoxy sugars, amino sugars, and acidic sugars

36
Q

what are sugar phosphates

A

phosphate esters

37
Q

what is the charge of sugar phosphates at neutral pH

A

negative

38
Q

what is the purpose of sugar phosphates

A

phosphorylation of sugar tends to trap sugar in a cell, as there aren’t many transporters for phosphorylated sugars

39
Q

what is a deoxy sugar

A

one of the OH groups is replaced with H

40
Q

what is an amino sugar

A

one of the OH groups is replaced with an amino group

41
Q

what is an acidic sugar

A

a carbon is oxidized (this will often be the aldehyde carbon)

42
Q

how are disaccharides produced

A

by condensing two monosaccharides into a glycoside with the formation of a covalent O-glycosidic bond

43
Q

in monosaccharide condensation, which parts of the monosaccharides interact

A

the OH of one sugar reacts with the anomeric carbon of the other

44
Q

what is maltose a major component of

A

dried cereal grains

45
Q

what is the structure of maltose

A

two D-glucose residues joined by an 1,4 alpha-glycosidic bond. The anomeric carbon of glucose on the left is locked in an alpha conformation while one on the right can freely rotate between a and b conformations

46
Q

what is lactose a major component of

A

milk

47
Q

what is the structure of lactose

A

D-galactose and D-glucose joined by an 1.4 beta-glycosidic bond

48
Q

describe lactose intolerance

A

arises from insufficient levels of lactase (which breaks down lactose). When the undigested lactose passes into the large intestine, high lactose concentration retains water, and the lactose is eventually fermented

49
Q

what is the structure of sucrose

A

D glucose and D fructose joined by an 1,2 glycosidic bond

50
Q

how is an N-glycosidic bond made

A

an N atom of a molecule can react with an anomeric carbon of a cyclic sugar

51
Q

how are nucleosidases made

A

with N-glycosidic bonds

52
Q

what is a homoglycan

A

a glycan with all the same monosaccharide subunit

53
Q

what is a heteroglycan

A

a glycan with different monosaccharide subunits

54
Q

what polysaccharides store glucose monomers for future cell respiration

A

starch and glycogen

55
Q

how is starch and glycogen stored in a cell

A

stored in large and heavily hydrated clusters or granules

56
Q

what are the two forms of starch

A

amylose and amylopectin

57
Q

describe the structure of amylose

A

unbranched polymer of 100-1000 D-glucose residues connected by (α1→4) glycosidic linkages

58
Q

describe the structure of amylopectin

A

branched, and branching occurs every 24-30 residues. Branches are attached via (α1→6) glycosidic bonds to linear chains of residues linked by (α1→4) glycosidic bonds. amylopectin may contain 300-6000 glucose residues

59
Q

describe the structure of a starch granule

A

it may have double helical chains of amylose/amylopectin and amylopectin/amylopectin.

60
Q

what happens to the structure of starch when fuels need to be mobilized

A

glucose molecules at the non reducing ends are enzymatically removed when fuels need to be mobilized

61
Q

describe the structure of glycogen

A

its a polymer of (α1->4) linked D-glucose subunits with (α1->6) branches. Its more branched + compact

62
Q

where in the body is glycogen mainly present

A

in the liver and skeletal muscle and cytosolic granules

63
Q

what happens to the reducing ends of glycogen

A

degradative enzymes hydrolyze glucose molecules from the non reducing ends of branches simultaneously

64
Q

give the formula for the number of glucose reducing ends available

A

n branches = n+1 reducing ends available

65
Q

why is glucose stored as glycogen

A

glycogen = insoluble while glucose = soluble. If we stored it as glucose, cell osmolarity would be high and water would rush in = cell bursts

66
Q

what is cellulose

A

tough, fibrous, and water insoluble glucose homoglycan. Its the major component of cell walls

67
Q

describe the structure of cellulose

A

linear unbranched glucose chains with a (β1->4) glycosidic linkage

68
Q

what are glycosidases

A

enzymes that catalyze the hydrolysis of glycosidic bonds, which is essential for sugar digestion

69
Q

describe the role of a-amylase

A

it’s an endoglycosidase: breaks internal glycosidic bonds for (α1→4) glycosidic linkages. It breaks downs starch and glycogen

70
Q

describe the role of cellulase

A

it’s an endoglycosidase: it breaks (β1→4) terminal glycosidic bonds in cellulose to release maltose

71
Q

describe the structure of chitin

A

a linear unbranched polymer. The monomers are N-acetylglucosamine (GlcNAc) linked by (β1→4) glycosidic linkages

72
Q

how are chitin bundles/fibrils formed

A

the GlcNAc residues of adjacent strands of chitin form hydrogen bonds with each other

73
Q

how do polysaccharides fold

A

a chain of monomers formed by covalent bonds will be stabilized into a shape by weaker interactions

74
Q

T or F: there is free rotation around the glycosidic linkage of polysaccharides

A

true; but steric hindrance limits the number of viable bond angles

75
Q

T or F: phi and psi angles can be used to describe the 3D polysaccharide structure and its dihedral angles

A

true

76
Q

what is the most stable structure for the α1->4 linked chains of starch and glycogen

A

a tightly coiled helix

77
Q

what is the most stable conformation of cellulose

A

where each glucose chair is 180 degrees from it’s neighbor, which produces a straight and extended chain with all OH groups available for H bonding to other chains

BIOL 2421 - Cellular Biochem (21 decks)

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