Lecture 1/2-Cell Organization Flashcards
What is the cytoskeleton made of and its importance?
Made of microtubules, intermediate filaments, micro filaments (actin filaments)
Used for:
1. Structural support & stability
2. Tracks for motor proteins to move organelles & vesicles within cells
Microtubules everything you need to know: require energy? diameter? polar? function?
LARGEST: hollow cylindrical tubes-25nm diameter
1. POLAR
2. Consist of globular (circular) subunits of alpha and beta tubulin
3. Takes 13 protofilaments to form 1 microtubule
4. Requires GTP
5. Function: independently-controls chromosomal movement, mitotic spindle for cell division, flagella/ciliar, intracellular transport
Grow from microtubule organizing center (MTOC) by polymerization
Microtubule-centriole and centrosome
- Centrioles consist of 9 triplets of microtubules arranged around a central axis-each triplet consists of 1 complete and 2 incomplete microtubules fused together
- 2 centrioles at 90 degree angle form a centrosome
- Located close to nucleus in non-dividing cells
- Provide basal bodies necessary for assembly of cilia and flagella
What are flagella made of and how is their movement produced?
- Consist of a core (axoneme)- 9+2 microtubule arrangement, pair of dynein arms
Movement: accessory proteins cross-link adjacent microtubules together which produces bending movement
Do primary cilia move?
NO MOVEMENT.
Arranged in a 9+0
Function as sensory antennae
1.** Photoreceptors** (outer segments of rods)
2. Chemoreceptors
3. Mechanoreceptors
Intracellular movement
ATP dependent
Done with Dynein and Kinesin
Dynein Family (3)
- Move in the negative direction (retrograde)
- Largest and fastest
- Binding sites for vesiciles, organelles or other microtubules
Kinesin Family (3)
- Move in the positive direction (anterograde)
- Binding sites for vesiciles, organelles or other microtubules
- ~40 distinct kinesins in humans
Intermediate Filaments: everything you need to know. Polar?How is formed? Energy required? Function?
- Non-polar
- First form dimers then tetramer and the 8 tetramers join to make a mature filament
- Provide structural support, essential for integrity of cell-cell & cell-ECM junctions
- No energy required
Used for tumor markings
Microfilaments (Actin filaments)
Function? Polar? Consist of? Require energy?
- May exist alone, in bundles or in networks
- SMALLEST
- POLAR
- G-actin: free actin molecules in the cytoplasm
- F-actin: polymerized actin in a filament
- Requires ATP
- Nucleation site-3 G-actin molecules each with a bound ATP
- For locomotion
- Anchorage and movement of membrane proteins (terminal web-apical surface of cells)
What are microvilli/stereocilia and what is their function?
- Increases surface area for absorption
- Stereocilia are much longer in length-found only in epididymis, proximal ductus deferens, sensory hairs in inner ear
Myosin movement
Cyclical in manner: Bind-hydrolyze ATP to ADP-detaches-binds again and repeats
-responsible for closure of gaps in wounds
-Active role in muscle contraction, cytokinesis
What are the three types of protusion structures based on actin organization?
- Filopedia-finger like projections
- Lamellipodia-sheet-like structure
- Pseudopodia-WBCs, 3 dimensional projections
Microfilament Cell Movement process (3 steps)
Think PACk for travel
- Protrusion-actin polymerization at the + end protrudes lamellipodium
- Attachment-focal adhesions anchor the actin cytoskeleton to the extracellular matrix via integrin proteins
- Contraction-bulk of the trailing cell & cytoplasm is drawn forward
Microtubule Poisons (3)
- Colchicine: Tx of GOUT-binds to unpolymerized tubulin molecules and prevents polymerization. Thus prevents release of inflammatory initiators
- Vinblastine and Vincristine: inhibit formation of mitotic spindle and uncontrolled cell division
- Taxol: stabilizes and prevents microtubule disassembly-arrests dividing cells in mitosis
