Cell Org III Flashcards
1
Q
name 3 major components of the cytoskeleton
A
- Actin filaments
- Intermediate filaments
- Microtubules
2
Q
describe the structure of microtubules (MT)
A
- Structure
- non-branching, rigid, hollow tubes
- Alpha and beta tubulin protein subunits
- Polar
- (-) end
- (+) end
- non-branching, rigid, hollow tubes
3
Q
describe the function of MT
A
- Intracellular transport
- Movement of vesicles and organelles
- Cell motility
- Movement of cilia and flagella
- Cell elongation and movement
- Mitotic spindle
- attachment of chromosomes and their movement during cell divison
- Rigid intracellular skeleton
- Maintenance of cell shape and polarity
- Assemble and disassemble as the needs of cell change
4
Q
describe structure of centrioles
A
- 9 triplets of MTs arranged around a central axis
- Each triplet consists of 1 complete and 2 incomplete MTs fused
5
Q
describe the function of centrioles
A
- Organize the centrosome
- Basal body formation
- Provide basal bodies necessary for assembly of cilia and flagella
- Mitotic spindle formation
- Formation of centrosome and alignment of the mitotic spindle during cell division
6
Q
what is the centrosome and describe the structure
A
- Centrosome is the microtubule organizing center (MTOC)
- Structure
- Contains a pair of centrioles at perpendicular angles
- Amorphous protein matrix
- >200 proteins
- Gamma-tubulin ring complexes
- Nucleating sites for MTs
7
Q
describe the function of centrosomes
A
- Organize MTs
- Initiate MT formation
- MTs are nucleated at the centrosome at their (+) end
- (+) ends point out and grow toward cell periphery
8
Q
describe mitotic spindle poisons (the first one)
A
- Colchicine
- anticancer compound
- Prevents polymerization
- Binds to unpolymerize tubulin molecules
- If given to dividing cells, mitotic spindle breaks down
- Programmed cell death
- Prevents polymerization
- Related compounds
- Vinca alkoids
- Vinblastine
- Vincristine
- Vinca alkoids
- anticancer compound
9
Q
describe the 2nd mitotic spindle poison
A
- Taxol
- Anticancer drug
- Stabilizes and prevents MT disassembly
- Preferentially binds tubulin within assembled MTs
- Arrests dividing cells in mitosis
- Unable to acheive metaphase sindle conformation
- Programmed cell death
- Stabilizes and prevents MT disassembly
- Anticancer drug
10
Q
Name the first MT motor famil
A
- Dynein family
- Move along MTs toward the (-) end
- 2 members
- Cytoplasmic dynein
- Axonemal dynein
- Cilia and flagella
- Binding sites for vesicles, organelles or another MT
- Largest anf fastest of the molecular motors
- 14 um/sec
11
Q
Name the 2nd motor family
A
- Kinesin Family
- Move along MT toward the (+) end
- 3 um/sec
- Binding sites for vesicles, organelles, MTs
- ~40 distinct kinesins in humans
- Move along MT toward the (+) end
12
Q
describe the structure and function of cilia
A
- MT-based, hair-like structure
- Motile
- Beat in synchronous pattern
- 9 + 2 MT arragement
- Pair of Dynein arms
- Motor protein
- Binds adjacent MT
- Move fluid and particles along epithelial surfaces
- Anchored to cell via the basal body
- Thin, dark-staining band at base of cilia
- Motile
13
Q
describe the structure and function of primary cilia
A
- MT-based, antennae-like structure
- 9 + 0 arrangement
- Emanates from almost all cells
- Anchored to cell via the basal body
- Develops from one centriole following cell division
14
Q
where are primary cilia located?
A
- Photoreceptors
- Outer segment of rods
- chemoreceptors
- odor detection by receptors on primary cilia of olfactory neurons
- Mechanoreceptors
- primary cilia of epithelial cells monitors the flow of fluid through the kidney tubules
- Defects underlie a variety of disorders
- Polycystic Kidney Disease
15
Q
describe the structure and function of intermediate filaments
A
- Formed from non-polar and highly variable subunits
- Functions:
- Stabilize cell structure
- Mechanical strength
- Maintain the position of the nucleus and other organelles
- Resist shearing forces
- extend across cytoplasm
- connecting with desmosomes and hemidesmosomes
- Stabilize cell structure
- Essential for integrity of cell-cell and cell-ECM junction
16
Q
name the 6 classes of IF
A
- 1 & 2: Keratins
- Acid and base cytokeratins
- Found in all epithelial cells
- Vimentin and vimentin-like
- Diverse family
- Most widely distributed in the body
- Vimentin
- Most abundant in mesoderm-derived cells
- Vimentin-like found in a variety of cells
- Desmin: muscle cells
- Glial fibrillary acid protein (GFAP): glial cells and astrocytes
- Diverse family
- Neurofilaments
- Extend from cell body into the ends of axons and dendrites
- 5: Lamins
- Found in nucleus of all nucleated cells
- Nuclear lamina
- Found in nucleus of all nucleated cells
- Beaded filaments
- Eye lens-specific group
17
Q
describe the structure and function of actin filaments (microfilaments)
A
- Polarzied structures
- Fast growing (+) end
- slow growing (–) end
- Function
- Anchorage
- Structural core of microvilli and stereocilia
- Cell motility
- locomotion
- Extension of cell processes
18
Q
name the 2 types of actin protein
A
- G-actin: free actin molecules in the cytoplasm
- F-actin: polyermized actin in a filament; ATP dependent
19
Q
which fungal products affect actin? (phalloidin)
A
- Phalloidin
- Toxin found in Amanita phalloides
- Disrupts normal function of actin
- Binds F-actin more tightly than G-actin
- Promotes excessive polymerization and inhibits depolymerization
- Inhibits cell movement
- Other toxins (amatoxins) are responsible for toxic effects following oral ingestion
- Liver and kidney failure and death 4-8 days after eating
20
Q
what does the fungus cytochalasins do to actin?
A
-
Block polymerization of actin
- Opposite of phalloidin, which promotes polymerization
- Can be used to inhibit cell movement, division and induce programmed cell death
21
Q
what are the actin motors?
A
- Myosin family
- Myosin II
- generates the force for skeletal muscle contraction
- Formed from 2 heavy chains and 4 light chains
- Tail-tail interactions result in formation of bipolar thick filaments
- Each head binds and hydrolyzes ATP
- Myosin II
22
Q
list the structural changes to myosin
A
- Stage 1: Attachment
- Rigor conformation
- Stage 2: Release
- ATP binds
- Reduces myosin affinity for actin
- Stage 3: Bending
- ATP hydrolysis
- Conformational change
- Stage 4: Force generation
- Weak binding of myosin to actin causes release of inorganic phosphate
- Release triggers binding and power stroke
- Force-generating conformational change
- Stage 5: Reattachment
- Rigor conformation
23
Q
describe the process of cell movment
A
- Protrusion
- actin polymerization at (+) end protrude lamellipodium
- Attachment
- focal adhesions anchor the actin cytoskeleton to the extracellular matrix via integrin proteins
- Contraction
- Bulk of the trailing cell and cytoplasm is drawn forward
