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Biochemistry > Chapter 10 (Exam 1 - in depth) > Flashcards

Chapter 10 (Exam 1 - in depth) Flashcards

1
Q

Why are carbohydrates named?

A

Because many have the formula Cn(H2O)n.

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2
Q

What can carbohydrates be covalently linked with?

A

Proteins and lipids.

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3
Q

What functions do carbohydrates fulfill?

A

Energy source and energy storage.
Structural component of cell walls and exoskeletons.
Informational molecules in cell-cell signaling.
Cellular identification.

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4
Q

What are monosaccharides?

A

Aldehydes or ketones that contain 2+ alcohol groups.

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5
Q

What are the smallest monosaccharides composed of?

A

3 carbons.

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6
Q

What is the basic nomenclature for naming carbohydrates?

A

Number of carbon atoms in the carbohydrate + -ose.
Example: three carbon = triose.

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7
Q

What are the common functional groups?

A

All carbohydrates initially had a carbonyl functional group.
Aldehydes = aldose.
Ketones = ketose.

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8
Q

What are the many isomeric forms monosaccharides exist in?

A

Isomers, constitutional isomers, stereoisomers, enantiomers, and diastereoisomers.
Epimers, anomers, diastereoisomers.

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9
Q

What are isomers?

A

Have the same molecular formula but different structure.

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10
Q

What are constitutional isomers?

A

Differ in the order of attachment of atoms.

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11
Q

What are enantiomers?

A

Stereoisomers that are nonsuperimposable mirror images.

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12
Q

What are stereoisomers?

A

Atoms are connected in the same order but differ in spatial arrangement.

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13
Q

What are diastereoisomers?

A

Isomers that are not mirror images.

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14
Q

What are epimers?

A

Differ at one of several asymmetric carbon atoms.

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15
Q

What are anomers?

A

Isomers that differ at a new asymmetric carbon atom formed on ring closure.

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16
Q

What are the common monosaccharides?

A

D-Ribose, D-Deoxyribose, D-Glucose, D-Mannose, D-Galactose, D-Fructose

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17
Q

What are the common carbohydrates in biochemistry?

A

Ribose, Glucose, Galactose, Mannose, Fructose.

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18
Q

What is ribose?

A

Standard 5-carbon sugar.

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19
Q

What is glucose?

A

Standard 6-carbon sugar.

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20
Q

What is galactose?

A

Epimer of glucose.

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21
Q

What is mannose?

A

Epimer of glucose.

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22
Q

What is fructose?

A

Ketose form of glucose.

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23
Q

What are D and L isomers of a sugar called?

A

Enantiomers.

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24
Q

What are most hexoses in living organisms?

A

D stereoisomers.

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25
Q

What form does L-arabinose occur in?

A

The L form.

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26
Q

What are D-Mannose and D-galactose?

A

Both epimers of D-glucose.
Each epimer differs from D-glucose in the configuration at one chiral center.

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27
Q

Where do D-Mannose and D-galactose vary at?

A

More than one chiral center and are diastereomers, but not epimers.

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28
Q

How do many common sugars exist in cyclic forms?

A

Chemical basis for ring formation is that an aldehyde can react with an alcohol to form a hemiacetal, whereas a ketone can react with an alcohol to form a hemiketal.

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29
Q

What do pentoses and hexoses readily undergo?

A

Intramolecular cyclization.

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30
Q

What is the anomeric carbon?

A

New chiral center that the former carbonyl carbon becomes.

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31
Q

What determines if the anomer of a monosaccharide is alpha or beta?

A

The position of the group when the former carbonyl oxygen becomes a hydroxyl group.

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32
Q

When is the configuration of a monosaccharide alpha?

A

If the hydroxyl group is on the opposite side (trans) of the ring as the CH2OH moiety.

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33
Q

When is the configuration of a monosaccharide beta?

A

If the hydroxyl group is on the same side (cis) of the ring as the CH2OH moiety.

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34
Q

Do pentoses and hexoses readily undergo intramolecular cyclization?

A

Yes.

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35
Q

What are 6-membered oxygen-containing rings called?

A

Pyranoses, after the pyran ring structure.

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36
Q

What are 5-membered oxygen-containing rings called?

A

Furanoses, after the furan ring structure.

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37
Q

What side is the anomeric carbon usually drawn on?

A

The right side.q

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38
Q

What does fructose form?

A

The pyranose form, which predominates when fructose is free in solution, and a furanose form, commonly seen in fructose derivatives.

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39
Q

What does a solution of glucose contain?

A

One-third alpha anomer, two-thirds beta anomer, and about 1% open chain.

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40
Q

Why does the free open chain of glucose react with oxidizing agents?

A

Because the 2 anomeric forms are in equilibrium that passes through an open chain form.

41
Q

What are reducing sugars?

A

Sugars that react with oxidizing agents.

42
Q

What are nonreducing sugars?

A

Sugars that do not react with oxidizing agents.

43
Q

What is an O-glycosidic bond?

A

Bond formed between the anomeric carbon atom and a hydroxyl group of another molecule.

44
Q

What is the glycoside?

A

Produce of an O-glycosidic bond.

45
Q

What is a N-glycosidic bond?

A

Bond formed between the anomeric carbon atom and an amine.

46
Q

What do carbohydrates form?

A

Ester linkages to phosphates.

47
Q

When does phosphorylation of sugars occur?

A

Routinely during metabolism.

48
Q

What are the common disaccharides?

A

Sucrose, lactose, and maltose.

49
Q

What do enzymes on the outer surface of intestinal epithelium do?

A

Cleave common disaccharides.

50
Q

What do sucrase, lactase, and maltase cleave?

A

Sucrase cleaves sucrose (table sugar).
Lactase cleaves lactose (milk sugar).
Maltase cleaves maltose.

51
Q

How many units do oligosaccharides consist of?

A

5 - 15 units typically.

52
Q

Where are oligosaccharides not commonly found?

A

Free in cells.

53
Q

What are oligosaccharides usually attached to?

A

Proteins.

54
Q

What is a glycoprotein?

A

Protein with small oligosaccharides attached.

55
Q

What type of proteins are glycoproteins?

A

About half of mammalian proteins.

56
Q

How is a carbohydrate attached to amino acids on the protein?

A

Via its anomeric carbon.

57
Q

How can attachments to proteins be linked?

A

N-linked (through asparagine) or O-linked (through serine or threonine).

58
Q

Where are O-linked sugars and N-linked sugars attached?

A

O-linked sugars: added in Golgi.
N-linked sugars: starts in ER and then completed in the Golgi.

59
Q

What do oligosaccharides function as?

A

Markers:
- Identity markers
- Destination markers.

60
Q

What are natural carbohydrates usually found as?

A

Polymers.

61
Q

What can polysaccharides be?

A

Homopolysaccharides (one monomer unit).
Heteropolysaccharides (multiple monomer units).
Linear (one type of glycosidic bond).
Branched (multiple types of glycosidic bonds).

62
Q

Why do polysaccharides do not have a defined molecular weight?

A

This is in contrast to proteins because, unliked proteins, no template is used to make polysaccharides.
Polysaccharides are often in a state of flux; monomer units are added and removed as needed by the organism.

63
Q

What types of homopolysaccharides?

A

Unbranched and branched.

64
Q

What are heteropolysaccharides?

A

Two monomer types, unbranched, and multiple monomer types, branched.

65
Q

What is glycogen?

A

A branched homopolysaccharide of glucose.

66
Q

What do glucose monomers form?

A

alpha1 –> 4 linked chains.
There are branch points with alpha1 –> 6 linkers every 8 - 12 residues.

67
Q

What is the molecular weight of glycogen?

A

Reaches several millions.

68
Q

What does glycogen function as?

A

Main storage polysaccharide in animals.

69
Q

Where is glycogen mostly found?

A

In muscles and liver.

70
Q

What are the common homopolymers of glucose?

A

Glycogen, starch, and cellulose.

71
Q

What is starch?

A

Mixture of 2 homopolysaccharides of glucose.

72
Q

What is amylose?

A

Unbranched polymer of alpha1 –> 4 linked residues.

73
Q

What is amylopectin?

A

Branched like glycogen, but the branch points with alpha1 –> 6 linkers occur every 24 - 30 residues.

74
Q

What is the molecular weight of amylopectin?

A

Up to 200 million.

75
Q

What is starch in plants?

A

The main storage polysaccharide.

76
Q

Why are glycogen and starch insoluble?

A

Due to their high molecular weight and often form granules in cells.

77
Q

What do granules contain?

A

Enzymes that synthesize and degrade these polymers.

78
Q

What do glycogen and amylopectin have?

A

One reducing end, but many nonreducing ends.

79
Q

When does enzymatic processing occur?

A

Simultaneously in many nonreducing ends.

80
Q

What is cellulose?

A

A linear homopolysaccharide of glucose.

81
Q

What do glucose monomers in cellulose form?

A

Beta1 –> 4 linked chains.

82
Q

What type of structure does cellulose have?

A

Tough and water insoluble.

83
Q

What is the most abundant polysaccharide in nature?

A

Cellulose.

84
Q

What is cotton?

A

A nearly pure fibrous cellulose.

85
Q

Why is cellulose a difficult substrate to act upon?

A

The fibrous structure and water insolubility.

86
Q

Why do most animals not use cellulose as a fuel source?

A

They lack the enzyme to hydrolyze Beta1 –> 4 linkages.

87
Q

What secretes cellulase and why?

A

Fungi, bacteria, and protozoa.
Allows them to use wood as a source of glucose.

88
Q

How do ruminants and termites live?

A

Symbiotically with microorganisms that produce cellulase and are able to absorb the freed glucose into their bloodstreams.

89
Q

What do Beta1,4 linkages favor?

A

Straight chains, which are optimal for structural purposes.

90
Q

What do Alpha1,4 linkages favor?

A

Bent structures, which are more suitable for storage.

91
Q

What is the structure of bacterial cell walls.

A

Linear polysaccharide chains are cross-linked by short peptides, pentaglycines, and tetrapeptides.

92
Q

What do bacterial cell walls consist of?

A

Peptidoglycans.

93
Q

What do bacteria cell walls contain?

A

D-amino acids. The cross-links of them are made by a mechanism different from the regular protein sythesis.

94
Q

What is Glycopeptide transpeptidase?

A

Enzyme involved in the formation of cross-links.

95
Q

What does Penicillin react with?

A

The active center of transpeptidase, and form an inactive complex, which is indefinitely stable. Penicillin is irreversible suicide inhibitor of transpeptidase.

96
Q

What is Chitin?

A

Linear homopolysaccharide of N-acetylglucosamine.

97
Q

What do N-acetylglucosamine monomers form?

A

Beta1 –> 4 - linked chains.

98
Q

What does chitin form?

A

Extended fibers that are similar to those of cellulose.

99
Q

Where is chitin found?

A

In cell walls in mushrooms and in exoskeletons of insects, spiders, crabs, and other arthropods.

Biochemistry (18 decks)

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