cytoskeleton Flashcards
how was the cytoskeleton discovered
Advances in microscopy enabled us to start seeing what was going on inside cells. Development of both types of microscopes enabled more detail to be seen. Molecular biology techniques used to differentiate different parts
why is the cytoskeleton described as dynamic
it is constantly changing e.g building up and breaking down
what roles do the cytoskeleton have
shape of the cell
movement of the cell
intracellular transport and rearrangement
communication inside cell and outside?
what are the cytoskeleton components and their purposes
actin (micro) filaments- cell movement and providing a force and produce the cleavage furrow
microtubules- cell organisation, movement and transport intracellularly
intermediate fibres- strength and protection
what is actin filaments made of
G-actin is the monomer and polymerise to form F-actin. When this happens ATP is hydrolysed to ADP, making f actin less stable. Made of two strands of G actin wound around each other
describe f actin
contains a plus end (barbed) and a minus end (pointed) due to having a direction.
The molecule will dissemble at the pointed end and grow at the barbed end
how does actin allow cell movement
a signal such as a nutrient source is received or a protein, this causes the large filamentous polymer to break down into its monomers which will diffuse to the direction of travel. They will then polymerise and cause movement.
How does actin have a role in cytokinesis
forms a contractile ring which can result in a cleavage furrow.
what are microtubules made up of
alpha beta dimers
outline the structure of microtubules
they are made up of protofilaments which run along the length of the cylinder. The protofilaments are made up of a b tubulin heterodimers which have a uniform orientation, resulting in a plus and minus end. the tubulin have a binding site for GTP which is hydrolysed into GDP when polymerised.
how are microtubules built up and regulated
polymerisation takes place to form a protofilament. It grows at the plus end quicker than at the minus end due to different critical concentrations. The beta dimer has its GTP hydrolysed to GDP which results in less stability as this reduces the affinity for adjacent molecules. This allows depolymerisation to take place. There tends to be a cap at the minus end.
How do microfilaments and microtubules differ
the microfilaments are smaller and are formed from two strands twisting around each other however the microtubules are hollow and made of strands of protofilaments. Both do ‘treadmilling’.
how are microtubules used for intracellular travel
minus end is attached to centriole and motor proteins move along in one direction. They do this by recognising the polarity of the strands. Dynein and kinesin are proteins which do this.
what properties do all intermediate fibres share
have a head and tail domain with long helical domain
form dimers which form tetramers. 8 tetramers coil around each other into a rope like filament
what is an example of where intermediate fibres go wrong
in epidermolysis Bullosa, the keratin gene in mutated which results in very fragile skin where any mechanical pressure can cause skin to break off
