Cytoskeleton Flashcards
What are the components of the cytoskeleton?
Microtubules
Microfilaments
Intermediate filaments
What are microtubules?
The largest and thickest elements of the cytoskeleton (25nm in diameter)
Long hollow tubes
What is tubulin?
A globular protein that has two versions, alpha and beta.
Alpha and beta tubulin bond to form AB dimer
What is a protofilament?
A chain of AB dimers
How many protofilaments form a hollow tube?
13 protofilaments
Where are microtubules assembled?
In the microtubule organizing center (MTOC)
What is the MTOC in animal cells?
The centrosome
What is the MTOC in plant cells?
It is unknown, but evidence shows that it is probably the nuclear envelope
What does the MTOC organize?
Centrioles, cilia, and flagella
What are centrioles?
Spindle-shaped bundles of microtubules located in the centrosome
How many microtubules do centrioles contain?
There are 9 sets of microtubule triplets in centrioles
What is dynein?
Filaments that form cross hatches/bridges between the microtubules
What do centrioles assemble?
Basal bodies located at the base of every cilium and flagellum
What do basal bodies assemble?
Cilia and flagella
What are cilia and flagella?
Basically the same thing. Used for movement. Blah blah blah
What is the difference between cilia and flagella?
Cilia are short and there are multiple of them on a cell
Flagella are long and there is typically one or two per cell
How many microtubules do cilia and flagella contain?
There are nine sets of microtubule doublets in cilia/flagella
What is an axoneme?
A structural and functional unit of ciliar/flagellar movement
What is the mechanism of ciliar and flagellar movement?
It is not well understood, but it is similar to the Sliding Filament Model in muscle cell contraction
What are microfilaments?
Smallest and thinnest element of the cytoskeleton
Structural support of the cell; cell movements
What is actin?
The most abundant protein in eukaryotic cells
What is alpha-actin?
What is G-actin?
Globular protein (idk what else to put uh)
What is F-actin?
Filament formed from two chains of G-actin coiled around each other
What is alpha-actin?
Actin found in skeletal muscle cells
What is tropomyosin?
Filamentous protein that runs along the outer edge of the F-actin filaments
What is the troponin complex?
A protein with three subunits that
1. attaches to troponin
2. attaches to tropomyosin
3. binds to Ca2+
What are intermediate filaments?
The medium-sized elements of the cytoskeleton (10nm in diameter)
What do intermediate filaments consist of?
Various rope-like fibrous proteins with tensile strength
What is tensile strength?
The resistance to being pulled apart
High tensile strength = hard to pull apart
What is the main function of intermediate filaments?
To enable cells to withstand mechanical stresses when stretched
What are the four types of intermediate filaments?
Keratin
Vimentin and desmin
Neurofilaments
Nuclear lamins
Where is keratin found?
In epithelial cells of vertebrates, especially in the skin (cytoplasm)
Where are vimentin and desmin found?
Found in connective tissue cells, muscle cells, and glial cells of nerve tissue
Where are neurofilaments found?
Found in neurons (cytoplasm)
Where are nuclear lamins found?
Found in nuclear envelope and strengthens it
