Flashcards in Cytoskeleton and cell structure Deck (15)
What is an organelle?
Any membrane limited structure found in the cytoplasm of the cell
What is the bio-membrane?
Permeability barrier that surrounding cells and organelles that consists of a phosphor- lipid bilayer, associated membrane proteins and in some cases cholesterol and glycolipids
What is the cytoskeleton?
System of protein filaments in the cytoplasm of a eukaryotic cell that gives the cell shape and the capacity for directed movement.
What are the 6 functions of the cytoskeleton?
I. Pulls chromosome apart at mitosis and splits the dividing cell in two.
II. Drives and guides intracellular traffic of organelles, ferrying materials from one part of the cell to another.
III. Supports the plasma membrane and mechanical linkages that bear the stresses and strains
IV. Enables some cells, such as sperm to swim, and others, such as fibroblasts and white blood cells to crawl.
V. Provides machinery in muscle cell contraction and in the neuron to extend an axon and dendrites.
VI. Summary- Varied functions of cytoskeleton centre on behaviour of 3 families of protein molecules.
What are actin filaments?
Function in maintenance of cell shape and in the control of cell attachment and motility
What are intermediate fibres?
Primarily involved in maintaining cell shape
What are microtubules?
Function in movement of organelles and participate with microfilaments in the control of cell movement
What is the structure of actin filaments?
Two stranded helical polymers of the protein actin.
Flexible structures, diameter approx 7nm.
Organised into a variety of linear bundles, two dimensional networks, and 3D semi solid gels.
Actin binding proteins.
Filaments dispersed throughout the cell, most highly concentrated in the cortex, just beneath the plasma membrane.
How does actin assemble?
Head to tail creating filaments that are polar and has a plus and minus
What are the regulation of cytoskeletal filaments?
Cell regulates length, stability, as well as number and geometry.
Cells regulate their attachments to one another and other components in the cell.
Most of this regulation is by accessory proteins that bind to either the filaments or free subunits
What is the organisation of actin filaments?
Organised in actin bundles and actin networks
The bundles are closely packed parallel arrays and the networks are loosely cross linked in arrays
Describe the intermediate filaments
Ropelike fibres with a diameter around 10nm.
Meshwork in the nucleus .
It extends across the cytoplasm giving mechanical strength.In epithelial tissue, span the cytoplasm from one cell-cell junction to another, strengthening the entire epithelium
What is the structure of tubular filaments?
Two closely related polypeptides
Long hollow cylinders that are more rigid than actin filaments
How does tubular assemble?
Head to tail creating filaments that are polar