Cytoskeleton Flashcards
What is the structure of the cytoskeleton?
Polymers/fibres joined by non covalent bonds.
What are the microfilaments (actin filaments) of the cytoskeleton?
F-actin and G-actin.
What is the main function of microfilaments?
Microfilaments assist with cell movement and are made of a protein called actin. Actin works with another protein called myosin to produce muscle movements, cell division, and cytoplasmic streaming.
What microtubules are in the cytoskeleton?
A and B-tubulin.
What are microtubules?
Microtubules are major components of the cytoskeleton. They are found in all eukaryotic cells, and they are involved in mitosis, cell motility, intracellular transport, and maintenance of cell shape. Microtubules are composed of alpha- and beta-tubulin subunits assembled into linear protofilaments.
What are the typical organisations of filaments within the cytoskeleton?
Intermediate Filaments
Microtubules
Actin filaments
What are the functions of the cytoskeleton?
Cell movement and motility.
Determination/maintenance of cell shape.
Polarity.
Intracellular transport.
Responsive to intracellular and extracellular signals.
Main factors of microtubules.
Localised throughout cell. Provide motorway system to all parts of cell body. Made of monomers a-tubulin and b-tubulin Used for cell motility. Consisting of 13 protofilaments.
Main factors of actin filament.
Localised at cel cortex.
Support of the plasma membrane.
Provide forces to move:
Muscle contraction
Main factors of intermediate filament.
Extend across cell cytoplasm.
Rope like.
Provide strength and structure.
Main factors of the Actin protein.
Each actin molecule has Mg2+ binding sites, with ATP/ADP bound.
Actin is present in both muscle and non muscle cells.
Describe the time course of actin polymerisation.
Nucleation (lag phase), elongation(growth phase) and then steady state (equilibrium phase).
Explain nucleation.
Nucleation; the initial process that occurs in the formation of a crystal from a solution, a liquid, or a vapour, in which a small number of ions, atoms, or molecules become arranged in a pattern characteristic of a crystalline solid.
Describe tubulin structure.
Polymers of A-B tubulin
Binding site for GTP, which is never hydrolysed or exchanged, so GTP is an integral part.
When does tubulin polymerisation reach a plateau phase?
Pure tubulin will polymerise into microtubules at 37°C in a test tube as long as Mg2+ and GTP are present, until a plateau is reached.
