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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
bone extracellular matrix
mainly of a rigid extracellular matrix containing a small number of interspersed cells
26
cartilage extracellular matrix
a tissue constructed mostly of matrix materials, more flexible than bones
27
connective tissue extracellular matrix
surrounding glands and blood vessels, relatively gelatinous and contains interspersed fibroblast cells
28
extracellular matrix consists of the same three classes of molecules
structural proteins protein-polysaccharide complexes adhesive glycoproteins
29
structural proteins
collagens, elastins, provide strength and flexibility
30
protein-polysaccharide complexes
proteoglycans, provide the matrix
31
adhesive glycoproteins
fibronectins, laminins, allow cells to attach to the matrix
32
collagens
a family of closely related molecules, which form fibers with high tensile strength, is secreted by several types of connective tissues
33
all collagens occur as
a rigid triple helix of intertwined polypeptides
34
collagens have an unusual composition
very high in glycine and rare amino acids hydroxylysine and hydroxyproline
35
collagen fibers
enormously strong, composed of numerous fibrils
36
fibrils
collagen molecule, composed of three a chains twisted into a helix
37
procollagen
three chains formed into a triple helix, with short nonhelical sequences at both ends
38
stability of collagen fibrils are reinforced by
hydrogen bonds within and between molecules
39
elastins
rich in glycine and proline, molecules are crosslinked by bonds between lysine residues
40
glycosaminoglycans (GAGs)
large carbohydrates with repeating disaccharide units, chondroitin, sulfate, keratan sulfate, hyaluronate
41
the disaccharide repeating unit of glycosaminoglycans
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
42
proteoglycans
vary greatly in size, depending on the size of the core protein and the length of the carbohydrate chains
43
direct links between the EMC and plasma membrane are reinforced by
adhesive glycoproteins, laminins, fibronectins
44
fibronectins
family of closely related glycoproteins, two large subunits linked by 2 disulfide bonds
45
effects of fibronectin
bridging molecules between cells and the ECM
46
laminins
found mainly in basal lamina
47
basal lamina
a think sheet of specialized extracellular material between the epithelial and connecitve tissues
48
enzymes that alter basal lamina
metalloproteinases (MMPs)
49
metalloproteinases (MMPs)
require metal ions as cofactors, degrade the ECM locally allowing cells to pass through
50
integrins
large family of cell surface receptors that bind to fibronectins or laminins, integrate the cytoskeleton with the ECM
51
structure of integrins
two large transmembrane polypeptides, alpha and beta differ in binding specificity and subunit sizes
52
focal adhesions
contain clustered integrins that interact with bundles of acti filaments via talin, vinculin, and a-actinin
53
hemidesmosomes
found in epithelial cells, contain a6b4 integrin attached to keratin, linker proteins form a dense plaque connecting integrins to the cytoskeleton
54
anchorage-dependent growth
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
costamere
an attachment structure at the surface of striated muscle
56
plant cell walls consist of
mainly long cellulose microfibrils enmeshed in a network of branched polysaccharides, pectins, hemicelluloses, and glycoproteins called extensins
57
plasmodesmata
cytoplasmic channels through openings in the cell wall, allowing cytoplasmic continuity between two adjacent cells
58
plasmodesmata function like
gap junctions
59
plasmodesmata structure
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
tropomyosin and troponin
regulate the availability of myosin-binding sites on actin filaments in a calcium-dependent manner
61
when calcium concentrations are low
tropomyosin blocks the myosin-binding sites on the actin filaments preventing interaction with myosin
62
when calcium concentration are high
calcium binds TnC causing tropomyosin to shift and allowing myosin to bind
63
nerve impulses from ______ ______ activate the appropriate muscle cells
motor neurons
64
neuromuscular junction
the site where a nerve contacts a muscle cell, conveying a signal to contract in the form of an action potential
65
axon terminals
make contact with the muscle cell
66
terminals store
acetylcholine, released in response to an action potential
67
when a receptor binds acetylcholine
it opens a voltage-gated channel in the membrane for inward Na+ flow
68
inward flow of sodium ions causes
membrane depolarization to be transmitted away from the motor end plate
69
transverse tubule system
via this system, membrane depolarization spreads through the sarcolemma
70
sarcoplasmic reticulum (SR)
poised to release calcium ions and then quickly remove them as needed
71
the SR has two functional components
medial element, terminal cisternae
72
SR medial element
contains calcium ATPase pumps
73
SR terminal cisternae
contain a high concentration of ATP-dependent Ca2+ pumps that can produce very high calcium concentrations in the lumen of the SR
74
SERCA
sarco/endoplasmic reticulum Ca2+-ATPases family, pumps calcium into the SR lumen, which can be released as needed
75
intercalated discs
have many gap junctions so waves of depolarization spread easily from one cell to the next
76
smooth muscle
responsible for involuntary contractions in various tissues, relatively slow contractions of greater duration
77
smooth muscle structure
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
when calcium concentration increases in smooth muscle
activated myosin light-chain kinase (MLCK)
79
myosin light-chain kinase
phosphorylates a regulatory light chain of myosin causing conformational changes allowing it assemble into filaments
80
smooth muscle contraction
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
cell crawling involves distinct events
1. extension of a protrusion 2. attachment to substrate 3, generation of tension
82
cell protrusion
extend from front or leading edge, during normal retrograde flow microfilaments move toward the rear of the protrusion as it ectends
83
lamellipodium
a thin sheet of cytoplasm
84
filopodium
a thin-pointed protrusion
85
retrograde flow
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
Arp2/3-dependent branching
drives actin polymerization, particularly in lamellipodia
87
Arp2/3-dependent branching
drives actin polymerization, particularly in lamellipodia
88
integrins on the outside of cells
attach to extracellular matrix proteins
89
integrins inside the cells
connect to actin filaments via linker proteins
90
focal adhesions
integrin-dependent attachments
91
cell contraction
contraction at the rear of the cell squeezes the cell body forward and releases the attachments at the rear
92
for movement to occur
new attachments must be balanced by loss of old ones
93
contraction is under the control of
Rho, which activates nonmuscle myosin II at the rear of the cell
94
amoeboid movement
involves cycles of gelation and solation of actin
95
gelation
as a pseudopodium is extended, more fluid material streams forward and congeals at the tip of the pseudopodium
96
solation
at the rear of the cell, cytosol changes to a more fluid state and streams forward
97
gelsolin
may be activated by calcium to convert the gel to a more fluid state
98
cytoplasmic streaming
an actomyosin-dependent movement of cytoplasm in the cell
99
elastins
rich in glycine and proline, the molecules are crosslinked by lysine residues
100
hyaluronate
an exception that occurs both as a backbone of cartilage proteoglycans and as a free molecule, has lubricating properties
101
laminin structure
three long polypeptides, alpha, beta, and gamma, several types of each can combine to form many types of laminin
102
hemidesmosomes
found in epithelial cells, contain alpha6beta4 integrin attached to keratin
103
bacteriophages
viruses that infect bacteria, attaches to the surface of the cell and injects material into it
104
lytic growth
injections, transcription, translation, self-assembly, and cell lyses; characteristic of virulent phages
105
temperate phage
can either produce lytic growth or integrate its DNA into the bacterial chromosome
106
DNA of a temperate phage
prophage
107
retroviruses

Cell Structure and Function (6 decks)

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