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Biochem > Chapter 8 > Flashcards

Chapter 8 Flashcards

1
Q

carbohydrates or … are the most abundant biological molecules.
they follow the chemical formula …

A

saccharides; (C * H2O)n

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2
Q

the basic carbohydrates units are called …

A

monosaccharides

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3
Q

monosaccharides are … or … derivatives of straight-chain polyhydroxy … containing at least 3 C atoms

A

aldehyde; ketone; alcohols

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4
Q

if the carbonyl group of a saccharide is an aldehyde, the sugar is an ..

A

aldose

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5
Q

if the carbonyl group of a saccharide is a ketone, the sugar is a …

A

ketose

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6
Q

the smallest monosaccharides, those with three C atoms, are … those with four, five, six, seven, etc. C atoms are, respectively, …, …, …, …

A

trioses; tetroses; pentoses; hexoses; heptoses

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7
Q

… sugars are biologically much less abundant than … sugars

A

L; D

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8
Q

D-glucose and … are epimers with respect to C2

A

D-mannose

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9
Q

the most common aldoses include the six-carbon sugars .., …, and …

A

glucose; mannose; galactose

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10
Q

the pentose … is a component of the ribonucleotide residues of RNA

A

ribose

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11
Q

the triose … occurs in several metabolic pathways

A

glyceraldehyde

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12
Q

the most common ketoses are …, … and …

A

dihydroxyacetone; ribulose; fructose

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13
Q

alcohols react with the carbonyl groups of aldehydes and ketones to form … and …, respectively

A

hemiacetals; hemiketals

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14
Q

the configurations of the substituents of each C atom in these sugar rings (cyclic hemiacetals/ketals) are conveniently represented by their …, in which the heavier ring bonds project in front of the plane of the paper and the lighter ring bonds project behind it

A

Haworth projectiosn

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15
Q

a sugar with a 6 membered ring is known as a … in analogy with …, the simplest compound containing such a ring

A

pyranose; pyran

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16
Q

sugars with five membered rings are designated … in analogy with ..

A

furanoses; furan

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17
Q

when a monosaccharide cyclizes, the carbonyl carbon, called the … carbon, becomes a … with two possible configurations

A

anomeric; chiral

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18
Q

the pair of stereoisomers that differ in configuration at the anomeric carbon care called .. in the alpha form, the OH substituent of the anomeric C is on the … side of the sugar ring from the CH2OH group at the chiral center that designates the D or L configuration. the other form is known as the … anomer

A

anomers; opposite; beta

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19
Q

the anomers freely interconvert in aqueous solution, a process called …

A

mutarotation

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20
Q

only … can simultaneously have all five of its non-H substituents in equatorial positions

A

beta-d-glucose

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21
Q

a monosaccharide can readily shift its …, bc no bonds are broken in the process. the shift in … between the alpha and beta forms requires breaking and reforming bonds and occurs slowly in aqueous solutoin

A

conformation; configuration

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22
Q

oxidation of an aldose converts its aldehyde group to a … group, thereby yielding an …

A

carboxylic acid; aldonic acid

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23
Q

oxidation of the primary alcohol group of aldoses yields …

ex. d-glucuronic acids

A

uronic acids

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24
Q

aldoses and ketoses can be reduced under mild conditions to yield polyhydroxy alcohols known as …
e.g. ribitol –> combonent of flavin coenzymes; xylitol–> sweetener used in ‘sugarless’ gum

A

alditols

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25
Q

monosaccharide units in which an OH group is replaced by H are known as … sugars
the biologically most important of these is …, the sugar component of DNA’s sugar-phosphate backbone.

A

deoxy sugars; beta-d-2-deoxyribose

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26
Q

in …, one or more OH groups have been replaced by an amino group, which is often acetylated
D-glucosamine and D-galactosamine are the most common

A

amino sugars

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27
Q

the anomeric group of a sugar can condense with an alcohol form … and …
the bond connecting the anomeric carbon to the alcohol oxygen is termed a …

A

alpha; beta-glycosides; glycosidic bond

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28
Q

saccharides bearing anomeric carbons that have not formed glycosides are termed …, because the free aldehyde group that is in equilibrium with the cyclic form of the sugar reduces mild oxidizing agents. the identification of a sugar as nonreducing is evidence that it is a …

A

reducing sugars; glycoside

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29
Q

polysaccharides, which are also known as …, consist of monosaccharides linked together by glycosidic bonds

A

glycans kk

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30
Q

polysaccharides are classified as … or … if they consist of one type or more than one type of monosaccharide

A

homopolysaccharides; heteropolysaccharides

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31
Q

polysaccharides, in contrast to proteins and nucleic acids, form … as well as … polymers

A

branched; linear

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32
Q

a complete description of an oligosaccharide or polysaccharide includes the .., … forms, and … of all its component monosaccharide units. some of this info can be gathered through the use of specific … and .., enzymes that hydrolyze monosaccharide units in much the same way that exopeptidases and endopeptidases cleave amino acid residues from polypeptides

A

identities; anomeric forms; linkages; exoglycosidases; endoglycosidases

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33
Q

the most abundant disaccharide is …

A

sucrose

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34
Q

…, the primary structural component of plant cell walls, accounts for over half of the carbon in the biosphere

A

cellulose

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35
Q

cellulose has a highly … structure that gives it exceptional strength and makes it … despite its hydrophilicity

A

cohesive; water insoluble

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36
Q

in plant cell walls, the cellulose fibers are embedded in and cross linked by a matrix containing other polysaccharides and …, a plasticlike phenolic polymer

A

lignin

37
Q

although vertebrates themselves do not possess an enzyme capable of hydrozlyzing the beta 1,4 linkages of cellulose, the digestive tracts of herbivores contain symbiotic microorganisms that secrete a series of enzymes, collectively known as …, that do so

A

cellulases

38
Q

… is the principal structural component of the exoskeletons of invertebrates such as crustaceans etc and is also present in the cell walls of most fungi and many algae. it is a homopolymer of beta 1–>4 linked N-acetyl-D-glucosamine

A

chitin

39
Q

… is a mixture of glycans that plants synthesize as their principal energy reserve

A

starch

40
Q

starch is deposited in the chloroplasts of plant cells as insoluble granules composed of … and …

A

alpha-amylose; amylopectin

41
Q

… consists mainly of alpha 1,4 linked glucose residues but is a branched molecule with alpha1,6 branch points every 24-30 glucose residues on average

A

amylopectin

42
Q

osmotic pressure is proportional to the number of … in a given volume

A

solute molecules

43
Q

starch is a reducing sugar, although it has only one residue, called the …, that lacks a glycosidic bond

A

reducing end

44
Q

… randomly hydrolyzes the alpha 1,4 glycosidic bonds of starch

A

amylase

45
Q

starch digestion is continued:
further hydrolysis by an …, which removes one glucose residue at a time, and by a … enzyme, which hydrolyzes alpha 1,6 and alpha 1,4 bonds, produces monosaccharides that are absorbed by the intestine and transported to the bloodstream

A

alpha-glucosidase; debranching enzyme

46
Q

…: storage polysaccharide of animals, most prevalent in skeletal muscle and liver

A

glycogen

47
Q

the primary structure of glycogen resembles amylopectin, but glycogen is more

A

highly branched

48
Q

glycogen is degraded for metabolic use by …, which phosphorolytically cleaves glycogen’s alpha 1,4 bonds sequentially inward from its nonreducing ends

A

glycogen phosphorylase

49
Q

glycogen’s highly branched structure, which has many … ends, permits the rapid mobilization of … in times of metabolic need

A

nonreducing ends; glucose

50
Q

the alpha 1,6 branches of glycogen are cleaved by

A

glycogen debranching enzyme

51
Q

…: unbranched polysaccharides that consist of alternating uronic acid and hexosamine residues

A

glycosaminoglycans

52
Q

… is an important glycosaminoglycan component of connective tissue, synovial fluid, and the vitreous humor of the eye

A

hyaluronic acid

53
Q

haparan sulfate plays a critical role in development and in wound healing. various … bind to heparan sulfate, and the formation of complexes of the glycosaminoglycan, the growth factor, and the growth factor receptor is required to initiate cell differentiation and proliferation

A

growth factors

54
Q

plants do not synthesize glycosaminoglycans, but the …, which are major components of cell walls, which also function as shock absorbers. they are heterogenous polysaccharides with a core of alpha 1,4 linked galacturonate residues interspersed with the hexose …

A

pectins; rhamnose

55
Q

…: an association of cells in a semisolid matrix

A

biofilm

56
Q

glycoproteins tend to have variable carbohydrate composition, a phenomenon known as …

A

microheterogeneity

57
Q

proteins and glycosaminoglycans in the extracellular matrix aggregate covalently and noncovalently to form a diverse group of macromolecules known as …

A

proteoglycans

58
Q

the polypeptide chains of glycoproteins are synthesized under …

A

genetic control

59
Q

glycoproteins tend to have variable carbohydrate composition, a phenomenon known as …

A

microheterogeneity

60
Q

characterizing the structures of carbs and their variations is one goal of the field of …, which complements the studies of genomics

A

glycomics

61
Q

proteins and glycosaminoglycans in the extracellular matrix aggregate covalently and noncovalently to form a diverse group of macromolecules known as …

A

proteoglycans

62
Q

proteoglycans have a bottlebrush0like architecture, with “bristles” noncovalently attached to a filamentous hyaluronate “backbone.” the bristles consist of a … to which glycosaminoglycans are covalently linked. the interaction btwn the core protein and the hyaluronate is stabilized by a …

A

core protein; link protein

63
Q

oligosaccharides glycosidically linked to the protein via the amide N of spefic Asn residues are known as

A

N-linked oligosaccharides

64
Q

oligosaccharides that are covalently bonded to side chain O atoms of specific Ser or Thr residues are …

A

O-linked oligosaccharides

65
Q

the extended brushlike structure of proteoglycans, together with the polyanionic character of their keratan sulfate and chondroitin sulfate components, cause these complexes to form …

A

highly hydrated gels

66
Q

bacteria are surrounded by rigid cell walls that give them their characteristic shapes and permit them to live in … environments

A

hypotonic

67
Q

bacterial cell walls are of considerable medical significance because they are in part responsible for bacterial

A

virulence

68
Q

bacteria are classified as … or … according to whether or not they take up Gram stain

A

gram-positive; gram-negative

69
Q

gram-positive bacteria have a … surrounding their plasma membrane, whereas gram-negative bacteria have a … covered by a complex …

A

thick cell wall; thin cell wall; outer membrane

70
Q

the cell walls of bacteria consist of covalently linked polysaccharide and polypeptide chains, which form a baglike macromolecule that completely encases the cell. this framework is known as …

A

peptidoglycan

71
Q

peptidoglycan’s polysaccharide component consists of linear chains of alternating beta 1,4 linked GlcNAc and …

A

N-acetylmuramic acid

72
Q

…, an enzyme present in tears, mucus, and other vertebrate body sections, catalyzes the hydrolysis of the beta 1,4 glycosidic linkage between N-acetylmuramic acid and N-acetylglucosamine

A

lysozyme

73
Q

almost all the secreted and membrane-associated proteins of eukaryotic cells are … oligosaccharides are covalently attached to proteins by either N-glycosidic or O-glycosidic bonds

A

glycosylated

74
Q

In …, GlcNAc is invariably beta-linked to the aminde nitrogen of an Asn residue in the sequence Asn-X-Ser or Asn-X-Thr, where X is any amino acid except Pro and only rarely Asp, Glu, Leu, or Trp

A

N-linked oligosaccharides

75
Q

N-glycosylation occurs …–that is, while the polypeptide is being synthesized

A

cotranslationally

76
Q

proteins containing N-linked oligosaccharides typically are glycosylated and then …

A

processed

77
Q

processing of n-linked oligosaccharides:
an oligosaccharide containing 9 mannose, 3 glucose, and 2 GlcNAc, is attached to the … of a growing polypeptide chain that is being synthesized by a ribosome associated with the ER
some of the sugars are removed during processing, which begins in the … (internal space) of the ER and continues in the Golgi apparatus. enzymatic trimming is accomplished by glucosidases and mannosidases

A

Asn; lumen

78
Q

n-linked oligosaccharides contd:
additional monosaccharide residues, including GlcNAc, galactose, fucose, and sialic acid, are added by the action of specific … in the Golgi

A

glycosyltransferases

79
Q

there is enormous … among the oligosaccharides of N-linked glycoproteins

A

diversity

80
Q

the most common O-glycosidic attachment involves the disaccharide core … linked to the OH group of either Ser or Thr

A

beta-galactosyl-1–>3-alpha-N-acetylgalactosamine

81
Q

o-linked oligosaccharides are synthesized in the … by the addition of monosaccharide units to a completed polypeptide chian.

A

Golgi apparatus

82
Q

…: the variant species of a glycoprotein

A

glycoforms

83
Q

since sugars are hydrophilic, the oligosaccharides tend to project away from the … bc carb chains are conformationally mobile, oligosaccharides attached to proteins can occupy time-averaged volumes of considerable size. in this way, an oligosaccharide can shield a protein’s …, possibly modifying its activity or protecting it from …

A

protein surface; surface; proteolysis

84
Q

the attachment of an oligosaccharide may help determine how the protein

A

folds

85
Q

the first evidence that unique combos of carbs might be involve din intracellular communication came with the discovery that all cells are coated with sugars in the form of … such as glycoproteins and glycolipids

A

glycoconjugates

86
Q

…: proteins that bind carbs, ubiquitous in nature and frequently appear on cell surfaces

A

lectins

87
Q

lectins are very specific: they can recognize individual … in particular linkages to other sugars in an oligosaccharide

A

monosaccharides

88
Q

proteins known as … mediate the attachment between leukocytes and the surfaces of endothelial cells

A

selectins

Biochem (23 decks)

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