Cytoskeleton Flashcards
What is the cytoskeleton?
Cytoskeleton—>network of fibres that extends throughout the cytoplasm
o Involved in maintaining and organizing structure of cell
What is cytosol?
> Cytosol: The semi-fluid portion of the cytoplasm
Cytosol—> h2O and dissolved ions, proteins, carbohydrates, nucleic acids
What are the roles of the cytoskeleton? (4)
• Mechanical support—> maintains shape
o Important in animal cells due to the lack of cell wall
• Provides anchorage for cell organelles
• Dynamic structure
o Can be disassembled, or de-polymerized, in one part of the cell and then reassembled in another part—> Changes the shape of the cell
• Involved in cell motility—> changes to cell location and movement of cell parts
o Requires interaction between cytoskeleton elements and motor proteins
o Above two work with the plasma membrane and cause cells to move along fibre networks outside of a cell
o Inside cells organelles and vesicles often use motor proteins to walk along tracks provided by the cytoskeleton to their destinations
What are the three components of the cytoskeleton?
• Cytoskeleton consists of three components:
- Microtubules—> the thickest of the three
- Microfilaments—> the thinnest of the three
- Intermediate filaments—> fall intermediate to the thickness of microtubules and microfilaments
What is the cytoplasm?
Cytoplasm:
> made from cytosol and cell organelles embedded within the cell cytoplasm
How is the cytosol separated?
> Cytosol is fundamentally separated from the organelles and their inner components as they are membrane-bound
The contents of the cell are bounded by the ____ membrane.
plasma
How does the cytoskeleton manipulate the cell membrane?
The cytoskeleton can also manipulate the cell membrane to form phagocytosis and hence form vacuoles from the invagination in the cell membrane engulfing a food particle or other.
Define what the cytoskeleton is?
Cytoskeleton: a network of microtubules, microfilaments and intermediate filaments that extend throughout the cytoplasm and serve a variety of mechanical, transport, dynamic and signal functions.
How are the cilia and flagella formed?
Cilia and flagella are formed fundamentally by sub-units made from the cytoplasm.
What is the nuclear lamina (lines the inner surface of the nuclear membrane)? (2)
> a dense fibrillar network inside the nucleus of most cell nuclei.
made up of many intermediate filaments and membrane-associated proteins that all work collectively to provide nucleus structures and anchorage (General mechanical support)
Microtubules
• Straight ____ rods
• 25nm in diameter and 200nm to 25um in length
• Are able to ______ move and reassemble
hollow
disassemble
What is the composition of microtubules?
Globular proteins: alpha-tubulin and beta-tubulin
What is the function of the microtubules? (3)
- Shape and support the cell
- Provide tracks along which organelles can move
- Cell motility
Where do microtubules grow out from?
Microtubules grow out from the centrosome
What are centrioles?
In the centrosome of the animal cells, there are a pair of centrioles
• Centriole is composed of 9 sets of triplet microtubules arranged in a ring
What do centrioles do?
Centrioles help organize microtubule assembly
What is the centrosome? (3)
- an organelle near the nucleus of a cell that contains the centrioles (in animal cells) and from which the spindle fibres develop in cell division.
- centrioles are found at right angles to each other; the centrosome is the microtubule origin site
- a set of microtubules triplets surround the inner cavity
What are the functions of the cilia and flagella?
motility of cells
Flagella are ____ structures and few in number, while cilia are ____ and numerous.
long
short
What is the structure of cilia and flagella? (2)
• Structure—> central core of two microtubules is surrounded by 9 doublets of microtubules
(9+2 pattern)
• Doublets have attached motor proteins, the dynein arms, that help bend the flagella
Size of microfilaments: solid rods approximately ___ in diameter.
7nm
What is the composition of microfilaments?
Composition—>built from two intertwined strands of actin, a globular protein
What is the function of microfilaments? (3)
- Aid in the contraction of muscles
- Microfilaments are attached to myosin
- Contraction of the cell results in actin and myosin microfilaments sliding past one another, this shortens the cell—>see muscle contraction (m line, z line, ADP, ATP, myosin, actin, myosin head)
How does muscle contraction work? (4)
> actin filaments (microfilaments) are connected to myosin filaments containing myosin heads
The myosin heads/ projections walk and causes the contraction of actin filaments parallel to the myosin movement
This causes muscle cell contractions
Muscle contraction involves many muscle cell contractions simultaneously and in sync
What is the size of intermediate filaments?
8-12nm in diameter
True or false
Intermediate filaments are more permanent structures than microtubules and microfilaments
True
What is the composition of intermediate filaments? (2)
- Several proteins like keratins
* Fibrous proteins coiled
What is the function of intermediate filaments?
• Providing structure to the cell, and anchoring of organelles within the cell
