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Cell Structure and Function > Exam 4 > Flashcards

Exam 4 Flashcards

1
Q

epithelium

A

sheets of polarized cells with discrete functional domains at opposite ends

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2
Q

connective tissue

A

more loosely organized, in which cells are attached to each other, a rigid scaffold, or both

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3
Q

cell-cell junctions

A

specialized structures where two cells come together

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4
Q

three types of junctions

A

adhesive junctions
tight junctions
gap junctions

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5
Q

plasmodesmata

A

special structures in plant cells

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6
Q

adhesive junctions

A

anchor the cytoskeleton to the cell surface, reply on specialized proteins

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7
Q

types of adhesive junctions

A

adherens junctions
desmosomes

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8
Q

adherens junctions

A

cadherin-mediated junctions that interact with actin; are especially prominent in epithelial cells

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9
Q

cadherins are characterized by

A

repeats in extracellular domain
a transmembrane domain
widely varying cytosolic ends

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10
Q

E-cadherins

A

has five repeats in extracellular domain, associate in pairs in the plasma membrane, cytosolic portions interact with B-catenin, a-catenin, and actin filaments

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11
Q

E-cadherins are found

A

epithelial cells

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12
Q

P-cadherins are found

A

placenta and other tissues

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13
Q

epithelial-mesenchymal transition (EMT)

A

the breakdown of epithelium into loosely organized mesenchyme cells

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14
Q

desmosomes

A

button-like points of strong adhesion between adjacent cells in a tissue, abundant in skin, heart muscle, and neck of the uterus

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15
Q

desmosome core

A

the extracellular space between the two connected cells

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16
Q

desmosomal cadherins

A

desmocollins and desmogleins

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17
Q

lectins

A

carbohydrate-binding proteins, promoting cell-cell adhesion by binding specific sugars at the outer cell surface, able to bind to two different cells

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18
Q

cell adhesion molecules (CAMs)

A

members of immunoglobulin super family, have well-organized loops in their extracellular domains, homophilic interactions occur via these domains

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19
Q

tight junctions

A

seal epithelial cells leaving no space between the plasma membrane of the adjacent cells

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20
Q

claudins

A

proteins with four membrane-spanning domains, thought molecules in adjacent cells interlock to form a tight seal

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21
Q

paracellular transport

A

large extracellular loop forms ion-selective pores and allow passage of specific ions, regulated by claudins

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22
Q

tight junctions block

A

lateral movement of lipids and proteins in the plasma membrane
lipids are only blocked by the outer monolayer
integral membrane proteins are completely blocked

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23
Q

gap junction

A

a region where the plasma membranes of cells are aligned and brought into contact, with a very small gap between them, has small pipelines between them, small molecules and ions can pass directly from one cell to another

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24
Q

connexons

A

hollow cylinders that join adjacent plasma membranes, assembly of six subunits to form a circle

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25
Q

bone extracellular matrix

A

mainly of a rigid extracellular matrix containing a small number of interspersed cells

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26
Q

cartilage extracellular matrix

A

a tissue constructed mostly of matrix materials, more flexible than bones

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27
Q

connective tissue extracellular matrix

A

surrounding glands and blood vessels, relatively gelatinous and contains interspersed fibroblast cells

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28
Q

extracellular matrix consists of the same three classes of molecules

A

structural proteins
protein-polysaccharide complexes
adhesive glycoproteins

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29
Q

structural proteins

A

collagens, elastins, provide strength and flexibility

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30
Q

protein-polysaccharide complexes

A

proteoglycans, provide the matrix

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31
Q

adhesive glycoproteins

A

fibronectins, laminins, allow cells to attach to the matrix

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32
Q

collagens

A

a family of closely related molecules, which form fibers with high tensile strength, is secreted by several types of connective tissues

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33
Q

all collagens occur as

A

a rigid triple helix of intertwined polypeptides

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34
Q

collagens have an unusual composition

A

very high in glycine and rare amino acids hydroxylysine and hydroxyproline

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35
Q

collagen fibers

A

enormously strong, composed of numerous fibrils

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36
Q

fibrils

A

collagen molecule, composed of three a chains twisted into a helix

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37
Q

procollagen

A

three chains formed into a triple helix, with short nonhelical sequences at both ends

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38
Q

stability of collagen fibrils are reinforced by

A

hydrogen bonds within and between molecules

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39
Q

elastins

A

rich in glycine and proline, molecules are crosslinked by bonds between lysine residues

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40
Q

glycosaminoglycans (GAGs)

A

large carbohydrates with repeating disaccharide units, chondroitin, sulfate, keratan sulfate, hyaluronate

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41
Q

the disaccharide repeating unit of glycosaminoglycans

A

has one amino sugar, either GlcNAc or GalNAc, and the other sugar is usually a sugar or sugar acid Gal or GlcUA, and the amino sugar has one or more sulfate groups attached

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42
Q

proteoglycans

A

vary greatly in size, depending on the size of the core protein and the length of the carbohydrate chains

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43
Q

direct links between the EMC and plasma membrane are reinforced by

A

adhesive glycoproteins, laminins, fibronectins

44
Q

fibronectins

A

family of closely related glycoproteins, two large subunits linked by 2 disulfide bonds

45
Q

effects of fibronectin

A

bridging molecules between cells and the ECM

46
Q

laminins

A

found mainly in basal lamina

47
Q

basal lamina

A

a think sheet of specialized extracellular material between the epithelial and connecitve tissues

48
Q

enzymes that alter basal lamina

A

metalloproteinases (MMPs)

49
Q

metalloproteinases (MMPs)

A

require metal ions as cofactors, degrade the ECM locally allowing cells to pass through

50
Q

integrins

A

large family of cell surface receptors that bind to fibronectins or laminins, integrate the cytoskeleton with the ECM

51
Q

structure of integrins

A

two large transmembrane polypeptides, alpha and beta
differ in binding specificity and subunit sizes

52
Q

focal adhesions

A

contain clustered integrins that interact with bundles of acti filaments via talin, vinculin, and a-actinin

53
Q

hemidesmosomes

A

found in epithelial cells, contain a6b4 integrin attached to keratin, linker proteins form a dense plaque connecting integrins to the cytoskeleton

54
Q

anchorage-dependent growth

A

must be attached to a substratum, if such cells cannot attach to an ECM layer, they stop dividing; involves activation of intracellular pathways following integrin clustering

55
Q

costamere

A

an attachment structure at the surface of striated muscle

56
Q

plant cell walls consist of

A

mainly long cellulose microfibrils enmeshed in a network of branched polysaccharides, pectins, hemicelluloses, and glycoproteins called extensins

57
Q

plasmodesmata

A

cytoplasmic channels through openings in the cell wall, allowing cytoplasmic continuity between two adjacent cells

58
Q

plasmodesmata function like

A

gap junctions

59
Q

plasmodesmata structure

A

lined with plasma membrane common to the two cells, with the desmotubule in the central channel
the annulus lise between the desmotubule and membrane lining the plasmodesma

60
Q

tropomyosin and troponin

A

regulate the availability of myosin-binding sites on actin filaments in a calcium-dependent manner

61
Q

when calcium concentrations are low

A

tropomyosin blocks the myosin-binding sites on the actin filaments preventing interaction with myosin

62
Q

when calcium concentration are high

A

calcium binds TnC causing tropomyosin to shift and allowing myosin to bind

63
Q

nerve impulses from ______ ______ activate the appropriate muscle cells

A

motor neurons

64
Q

neuromuscular junction

A

the site where a nerve contacts a muscle cell, conveying a signal to contract in the form of an action potential

65
Q

axon terminals

A

make contact with the muscle cell

66
Q

terminals store

A

acetylcholine, released in response to an action potential

67
Q

when a receptor binds acetylcholine

A

it opens a voltage-gated channel in the membrane for inward Na+ flow

68
Q

inward flow of sodium ions causes

A

membrane depolarization to be transmitted away from the motor end plate

69
Q

transverse tubule system

A

via this system, membrane depolarization spreads through the sarcolemma

70
Q

sarcoplasmic reticulum (SR)

A

poised to release calcium ions and then quickly remove them as needed

71
Q

the SR has two functional components

A

medial element, terminal cisternae

72
Q

SR medial element

A

contains calcium ATPase pumps

73
Q

SR terminal cisternae

A

contain a high concentration of ATP-dependent Ca2+ pumps that can produce very high calcium concentrations in the lumen of the SR

74
Q

SERCA

A

sarco/endoplasmic reticulum Ca2+-ATPases family, pumps calcium into the SR lumen, which can be released as needed

75
Q

intercalated discs

A

have many gap junctions so waves of depolarization spread easily from one cell to the next

76
Q

smooth muscle

A

responsible for involuntary contractions in various tissues, relatively slow contractions of greater duration

77
Q

smooth muscle structure

A

long, thin with pointed ends and no striations, have dense bodies instead of Z lines
bundles of actin and myosin filaments are anchored at both ends to the dense bodies

78
Q

when calcium concentration increases in smooth muscle

A

activated myosin light-chain kinase (MLCK)

79
Q

myosin light-chain kinase

A

phosphorylates a regulatory light chain of myosin causing conformational changes allowing it assemble into filaments

80
Q

smooth muscle contraction

A
  1. extracellular calcium enters the muscle cell
  2. increased Ca2+ concentration activated calmodulin
  3. the calcium-calmodulin complex binds to MLCK and triggers myosin light-chain phosphorylation
  4. myosin light-chain phosphatase removed the phosphate and the muscle cells relax
81
Q

cell crawling involves distinct events

A
  1. extension of a protrusion
  2. attachment to substrate
    3, generation of tension
82
Q

cell protrusion

A

extend from front or leading edge, during normal retrograde flow microfilaments move toward the rear of the protrusion as it ectends

83
Q

lamellipodium

A

a thin sheet of cytoplasm

84
Q

filopodium

A

a thin-pointed protrusion

85
Q

retrograde flow

A

results from actin assembly at the growing tip of the protrusion and rearward translocation of filaments toward. the base of the protrusion powered by myosin

86
Q

Arp2/3-dependent branching

A

drives actin polymerization, particularly in lamellipodia

87
Q

Arp2/3-dependent branching

A

drives actin polymerization, particularly in lamellipodia

88
Q

integrins on the outside of cells

A

attach to extracellular matrix proteins

89
Q

integrins inside the cells

A

connect to actin filaments via linker proteins

90
Q

focal adhesions

A

integrin-dependent attachments

91
Q

cell contraction

A

contraction at the rear of the cell squeezes the cell body forward and releases the attachments at the rear

92
Q

for movement to occur

A

new attachments must be balanced by loss of old ones

93
Q

contraction is under the control of

A

Rho, which activates nonmuscle myosin II at the rear of the cell

94
Q

amoeboid movement

A

involves cycles of gelation and solation of actin

95
Q

gelation

A

as a pseudopodium is extended, more fluid material streams forward and congeals at the tip of the pseudopodium

96
Q

solation

A

at the rear of the cell, cytosol changes to a more fluid state and streams forward

97
Q

gelsolin

A

may be activated by calcium to convert the gel to a more fluid state

98
Q

cytoplasmic streaming

A

an actomyosin-dependent movement of cytoplasm in the cell

99
Q

elastins

A

rich in glycine and proline, the molecules are crosslinked by lysine residues

100
Q

hyaluronate

A

an exception that occurs both as a backbone of cartilage proteoglycans and as a free molecule, has lubricating properties

101
Q

laminin structure

A

three long polypeptides, alpha, beta, and gamma, several types of each can combine to form many types of laminin

102
Q

hemidesmosomes

A

found in epithelial cells, contain alpha6beta4 integrin attached to keratin

103
Q

bacteriophages

A

viruses that infect bacteria, attaches to the surface of the cell and injects material into it

104
Q

lytic growth

A

injections, transcription, translation, self-assembly, and cell lyses; characteristic of virulent phages

105
Q

temperate phage

A

can either produce lytic growth or integrate its DNA into the bacterial chromosome

106
Q

DNA of a temperate phage

A

prophage

107
Q

retroviruses

A

Cell Structure and Function (6 decks)

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