Cytoskeleton Flashcards
What are the 3 filaments of the cytoskeleton?
Microfilaments
Intermediate filaments
Microtubules
What are the functions of microfilaments?
Whole-cell movement
Muscle contraction
Cell shape
Cytokinesis
What is the function of intermediate filaments?
Strength
What are the functions of microtubules?
Movement of cilia and flagella
Intracellular trafficking
Mitotic spindle formation
What is the central component of microfilaments and how is it formed?
Actin
G-actin monomers polymerize into F-actin microfilament using ATP
What are the functions of actin?
Structural and motility systems
Maintain cell shape
Support for plasma membranes and its protrusions
Restricts diffusion of organelles
Anchor for cell adhesion molecules
Contraction (myosin) in muscle cells
Actomyosin ring in telophase of mitosis
How do cells migrate on ECM with actin?
Leading edge attaches and back edge releases
Important during embryogenesis and growth
What are thin filaments?
Mainly F-actin, particularly in muscle cells
Tropomyosin
Troponin complex (skeletal and cardiac cells)
What is myosin?
Thick filament
Actin-binding motor protein
Binds ATP
Muscle and non-muscle cells
What is the function of intermediate filaments?
Mechanical strength
What are the major types of intermediate filaments?
Keratins
Vimentins
Neurofilaments
Lamins
Nestin
Where keratins found and what is there function?
In cytosol of epithelial cells
Interconnect desmosomes
Strong adhesion between epithelial cells and underlying ECM
What are the functions of neurofilaments?
Structural support in nerve axon to resist breakage
What is vimentin and its function?
Includes desmin and vimentin
In mesoderm-derived cells, widely distributed
Desmin in muscle cells - stabilize contractile apparatus
Where are lamins found and what are their function?
Only in nuclei
Line inner nuclear surface
Protect chromatin from mechanical stress
Support nuclear envelope
Dissemble at mitosis
Where is nestin found and what is its function?
Widely expressed, particularly neural progenitor cells
Associated with cell proliferation
What is the structure of microtubules?
Cytosolic
Hollow
Polar
Cylinders
Alpha and beta tubulin heterodimers
What are the functions of microtubules?
Motility (cilia and flagella)
Chromosomal movements during cell division
Transport of intercellular vesicles
How to microtubules redirect traffic?
By disassembling in one region and assembling in another
What is a centrosome and its function?
Composed of 2 centrioles and pericentriolar material
Origin of microtubules, cap minus end
What is dynamic instability of microtubules?
Assembly then breakdown - rapid
Tubulin bound to GTP add at plus end
Disassembly from plus end - prevented by capping
What is vesicle and organelle transport?
Requires ATP and microtubule motor proteins (ATPases)
Kinesin - anterograde
Cytoplasmic dynein - retrograde
How do cilia and flagella move?
Axoneme - 9+2 extending from basal body anchored in plasma membrane
Axonemal dynein - ATPase
Stable microtubules resist breakdown
What is the function of microtubules in mitosis?
Two centrosomes
