Ma - Cell Organelles Ii

Front 1

Cytoskeleton Components (3)

Back 1

Our cells have a cytoskeleton of (in order of decreasing diameter) microtubules, intermediate filaments, and actin (micro) filaments. Make a very complex meshwork, dicate shape, and allows movement of cells and organelles.
The system is similar to our body's endoskeleton of bones, cartilages, and ligaments/tendons.

Front 2

Size and Structure of Microtubules (4)

Back 2

1) 20-25 nm tubules, 13 protofilaments of tubulin dimers
2) Tubulin dimer has 1 alpha-tubulin + 1 beta-tubulin arranged head to tail
3) Microtubule organizing center (at - end of microtubule) has capping proteins and gamma-tubulin.
4) GTP-tubulin dimers assemble into GDP-dimers + Pi

Front 3

Function and Organization of Microtubules (5)

Back 3

1) Maintain shapes of cells-axons, Sertoli cells, peripheral band in platelets
2) Organized into Mitotic Spindle
3) Organized into centrioles, cilia, and flagella
4) Used in Intracellular Transport Pathways
5) Have Dynamic Instability - assemble and disassemble for various functions

Front 4

Kinesins and Dyneins

Back 4

Both at ATPases.
Kinesins are bivalent proteins on microtubules that have 2 sites: 1 site recognizes other microtubules and the other recognizes endocytic vesicles. Kinesins move these across the cell.
Dyneins recognize microtubules , lysoomes, and mitrochondria and move them across cell. When dynein arms are missing on cilia & flagella, they can't move the molecule (like sperm)

Front 5

Actin Filaments (Microfilaments) Size and Structure (5)

Back 5

-Ubiquitous, 6-8 filaments, composed of 42 kDa G-actin subunits polymerized into F-actin
-G-actin-ATP ---> F-actin-ADP + Pi (consumes ATP)
-Have + (fast growing) and - ends
-In microvilli, filaments are bundled and stabilized by fascin and fimbrin
-Actin gels dissolve at high Ca+2 by fragmentation by gelsolin.

Front 6

Microfilament Arrangements (2)

Back 6

-Arranged into formal paracrystalline arrays in Muscle, and associated with regulatory protein Troponin and Tropomyosin.
-Form Thin Filaments of skeletal and cardiac muscle. These Thin Filaments are F-actin + regulatory proteins.

Front 7

Intermediate Filaments Size and Structure

Back 7

- 8-10 nm rope-like aggregates of monomers
-Provide generic structural support of cells
-Many varieties: all chemically related but distinct chemically
-Probably stable (more so than microtubules and microfilaments). But all 3 collabo to make cytoskeleton

Front 8

Types of Intermediate Filaments (4)

Back 8

1)Keratins - found in many epithelial cells (fingernails, hair, skin, dead cells being brushed off full of it) - form support for desmosomes-many varieties.
2) Vimentin family: Vimentin (many CTs), desmin (muscle), GFAP (glia)
3) Neurofilaments - neurons
4) Lamins - nuclear envelope

Front 9

Clinical Considerations Relevant to Disruptions in Cytoskeleton (5)

Back 9

1) Colchicine - Gout (usually in 60+ years of ppl w/ bad habits)
2) Vinblastine and taxol - Cancer Chemotherapy - inhibits microfilament and microtubule formation respectively.
3) Phalloidin-actin filaments - Mushroom Poisoning
4) GFAP - Alzheimer Disease - accumulation of certain glial cells in brain-->neurons work less-->memory loss
5) Mallory bodies (keratin) - Alcoholic Cirrhosis - accumulation of intermediate filaments

Front 10

Centrioles - Location, Structure, Organization, Function (5)

Back 10

-Usually found near nucleus in centrosome or MTOC
-Pair of small cylinders composed of 9 Microtubule Triplets
-Organized at right angles to one another
-Replicate before mitosis and form opposite end of mitotic spindle
-Organize Mitotic Spindle