Nucleus & Cytoskeleton Flashcards
(89 cards)
1
Q
Chromatin
A
Genetic material that contains DNA assoc. w/ nuclear proteins
2
Q
Is chromatin acid or basophilic?
A
Basophilic
3
Q
Euchromatin
A
Loosely packed, pale staining, active chromatin where majority of transcribed genes are located
4
Q
Marginal chromatin
A
Heterochromatin at periphery of nucleus near nuclear envelope
5
Q
Karyosomes
A
Heterochromatin in discrete bodies suspended in nucleoplasm
6
Q
Amount of euchromatin is proportional to ___
A
Metabolic activity of cell
7
Q
Heterochromatin
A
Tightly coiled, darkened, inactive, classified by location
8
Q
Nuclear-associated chromatin
A
Heterochromatin associated w/ nucleus
9
Q
Barr body
A
Inactive, heterochromatic, 1 of 2 X chromosomes in female cells in interphase nucleus
10
Q
Where are Barr bodies seen?
A
Neutrophils or epithelial cells scraped from inside of cheek
11
Q
Pyknotic nuclei
A
Condensed, darkly stained nuclei w/ small amt euchromatin
12
Q
Vesicular
A
Open-faced, pale-staining active nuclei where euchromatin prevails
13
Q
Euchromatin are _____rich whereas heterochromatin are ___rich
A
Gene-rich, repeat-rich
14
Q
Nucleolus
A
. Where rRNA synthesis and initial ribosomal assembly is (contains rRNA and proteins)
. Basophilic
. Cells can have multiple
15
Q
Where are nucleoli well developed?
A
Cells active in protein synthesis
16
Q
Nuclear envelope
A
. Has outer and inner membrane separated by pernicious space/cisterna
17
Q
outer layer of nuclear envelope
A
Continuous w/ RER
18
Q
Inner membrane of nuclear envelope
A
Supported by nuclear lamina
19
Q
Nuclear lamina components
A
Intermediate filaments (lamins)
20
Q
Nuclear pores
A
.Openings in nuclear envelope associated w/pore complex
21
Q
Nuclear pore complex
A
Facilitates and controls highly selective transport between cytoplasm and nucleus
22
Q
What happens to nuclear envelope in cell division?
A
It is disassembled during division and then rebuilt after division is completed
23
Q
Laminopathies
A
Diseases link to defect in proteins of nuclear envelope (lamins) affecting skeletal and cardiac muscle, nerves, and adipose tissue
24
Q
Interphase stages
A
G1, S, G2
25
G1 in interphase
. Time gap between mitosis and DNA replication
26
G0 state
Cell begin to differentiate but don’t progress into S phase, but suspend all cell activity
27
S phase
DNA and chromosome-associated protein synthesis and centriole replication
28
G2 phase of interphase
Gap between DNA replication and mitosis
29
Can chromosomes be seen in nucleus in interphase?
No, seen ass euchromatin and heterochromatin
30
Mitosis
DNA condenses into chromosomes, nuclear envelope and nucleolus disappear
31
Mitosis figures
LM image nuclei w// condensed chromosomes
32
When are condensed chromosomes visible in LM?
Late prophase, metaphase, anaphase, and telophase
33
Cytoskeleton
System of proteins that supports internal cell architecture and adds in movement of organelles and transport of vesicles as well as cell locomotion and sensing
34
Microtubule characteristics
. Hollow tubes of tubulin
. Rapidly row in length or disassemble as tubulin is added or removed
. Form centrioles and mitosis spindle
35
Microtubule structure
. Tubulin dimers form helix w/ 13 molecules in 1 turn
| . outer diameter is 24 nm and hollow core is 14 nm
36
Tubulin structure
Protein with Alpha and beta subunits
37
Where are microtubules found?
Cytoplasm growing from microtubule organizing center (MTOC) or in cilia, flagella, and growing neuron axons
38
Colchicine
Cancer therapy that prevents tubulin polymerization
39
Taxol
Cancer therapy that prevents microtubule depolymerization
40
Functions of microtubules
. Intracellular vesicular transport
. Movement (cilia/flagella or chromosomes during division)
. Cell elongation and locomotion
. Maintenance of cell shape
41
Centrioles
. Paired short (0.2 um) cylinders
. 2 per cell laying right angles to each other in MTOC
. Duplicate before division
42
Centriole structure
Cylinders made of 9 triplets of microtubules that run parallel to long axis and are slightly twisted
43
Centriole duplication and location
. New centriole formed at right angle next to existing centriole
. Separate and move to opposite cell poles to be center of mitosis spindle formation
44
Centriole functions
. MTOC formation
. Mitotic spindle formation during cell division
. Basal body formation of cilia and flagella
45
Basal bodies
Structurally similar to centrioles, formed by migrating centrioles after replication to apical cell surface
46
Actin filaments
. Also called microfilaments
. 5-7 nm Polymers of actin molecules
. In ALL eukaryotic cells
47
Actin filaments functions
. Formation of 3D skeleton w/in cell
. Part of specialized cell junction
. Structural support of microvilli (core and terminal web)
. Cell locomotion
. Associates w/ microtubules to produce outgrowths of neuronal cell processes
48
Intermediate filaments
. 10-12 nm, structural role
. More stable than microtubules and actin filaments
. Absorbs mechanical stress
49
Intermediate filament structure
. Assemble from subunits
| . High degree of heterogeneity and tissue specificity
50
Types of intermediate filaments
Keratin, lamins, vimentin, Desmond, and a family of neurofilaments
51
Clinical significance of intermediate filaments
Antibodies to specific intermediate filaments useful in defining origins of metastatic cancer cells
52
Cell junctions
. How cells are connected to each other and attached to extra cellular matrix (ECM)
. Facilitate adhesion and communication btw cells
53
Cell adhesion molecules (CAMs)
Enable cells to attach to one another and ECM
54
Where are cell junctions prominent?
Epithelial cells
55
Types of cell junctions
Tight/occluding, adherent, intermediate, desmosomes, and hemidesmosomes
56
Zonulae occludens
. Tight junctions
. Cell membranes of adjacent cells come together at regular intervals to seal apical intercellular space
. Surround entire surface of cell (belt-like)
. Assoc. w/ actin filaments
57
CAMs in tight junction formation
Occluding and Claudin (transmembrane)
58
Adherent/anchoring junctions
Types of cell junction
59
Zonulae adherens
```
. Intermediate junctions
. Surround entire cells
Intercellular space is present
. Found below tight junctions near apicla surface of epithelial cells
. Connected to actin cytoskeleton
```
60
formation of zonulae adherens
E and PCadherin CAMs binds to intracellular catenins to link actin filaments from adjacent cells across apical cytoplasm (TERMINAL WEB)
61
Maculae adherens
. Desmosomes
. Spot-like junctions
. Disc structures at lateral surface of cells
. In epithelial and cardiacs muscle cells
. Intercellular space present
62
Maculae adherens formation
Desmoglein and desmocollin CAMs bind to intracellular attachment plaque that binds to intermediate filaments
63
What is attachment plaque used by desmosome CAMS made up of?
Plakoglobin and desmoplakin
64
Keratin filaments
Also called tonofilaments, intermediate filaments of epithelial cells
65
Hemidesmosomes
. Unilateral junctions anchoring basal domain of epithelial cel to ECM
. Assoc. w/ keratin intermediate filaments
66
Gap junctions
. Allow direct communication between adjacent cells via diffusion
. Prominent in epithelia, smooth and cardiac muscle, neural and bone cells\\\\\\\\\\\\\\\\\\\\\\\\\
67
Gap junction formation
. 6 connexin monomers form connexon
. 2 connexons from adjacent cells align to form channel
. Connexons form large clusters
68
What opens and closes gap junctions?
Conformational changes in connexins
69
Connexin
Integral membrane proteins
70
Connexon
. Hollow cyndrical hemichannel that spans plasma membrane
| . Composed of 6 connexins
71
T/F ALL channels in connexon clusters are active
F, as few as 20% can be active
72
Where are connexins NOT expressed?
Sperm and adult skeletal muscle
73
Gap junctions are important in tissues involved in _____
. Early embryonic development
. Myocardial electrical and contractile activity
. Smooth muscle contraction
74
Blistering diseases are often caused by ____
Abnormal desmosome function
75
Mutations in connexin genes are assoc. w/ ____
Deafness, congenital cataracts, demyelinating neuropathies, and skeletal defects
76
Apoptosis
. Programmed cell death eliminating defective or no longer needed cells
. Not associated w/ inflammation
77
how is apoptosis controlled?
. Bcl-2 protein family
78
Apoptosis process
. Cytochrome c released from mitochrondria into cytoplasm after signal activating caspases to take apart cells
. Cell and nucleus shrink (pyknotic)
. Fragment into apoptotic bodies (membrane-enclosed) removed via phagocytosis
79
Cascades
Proteolytic enzymes that take apart cell content
80
Necrosis
. Nonphysiologic process as result of cell injury
. Cell swelling and lysis
. Assoc. w/ inflammation and tissue damage
81
Constitutive heterochromatin
Repetitive, gene poor DNA (centromeres and telomeres)
82
Facultative heterochromatin
DNA with genes variably inactivated (BARR BODY)
83
Hutchinson-Guilford Progeria Syndrome (HGPS)
. Accelerated aging
. Growth failure, skin aging, joint stiffness, stroke
. From Lamin mutation
84
Kinesin function
From cell body outside (anterograde) transport
85
Dyeins function
Retrograde (back into cell) transport
86
Vimentin
Intermediate filaments in fibroblasts
87
Desmin
Intermediate filaments in striated muscle
88
Terminal bar
Junction made up of zonula occludens, zonula adherens, and macula adherens
89
Epithelial neoplasia
. Down regulation of E-cadherin in zonula adherens
. Loss of cell-cell adhesion and cell polarity
. Migratory cells that normally don’t migrate
