L3. Cytoskeleton Flashcards
3 types of cytoskeleton?
- Microfilament - actin
- Intermediate filament
- Microtubule
How does 3 types of cytoskeleton structured in the cell?
- Actin filament - meshed-shape in the peripheral of cell
- Intermediate filament - connects to cell together so wrap from the point on the cell membrane towards the middle of cell
- microtubule - grow from the centrosome
Function of Actin filament
- To move the cell as whole
- cell division
- shape and substructure of cell
The structure and polymerisation of actin
- monomer : G-actin (globular actin)
- G-actin plomerise into F-actin
- The monomer binds together from +end to -end
- Addition of subunits can happen at both ends, but it happens faster at the + end; thus, individual actin molecules seem to migrate from the barbed to the pointed end = actin treadmilling
1. G-actin reversibly polymerises into double-helical fibres = F-actin =
The function of myosin
- muscle contraction
- Cargo transportation
It’s a motor protein, which have 2 types:
1. myosin 1 will bind to acti
Actin-based structures in motile cells
- Stress fibres Contractile actin-myosin bundles in the cytoplasm → need contractile action to move the cell
- LamellipodiumThin, sheet-like extension that contains dense meshwork of actin filaments → they projecting forward to enabling the whole cell to move forward
- FilopodiaTransient finger-like protrusions that contains loose bundles of actin filaments → helps the cell to navigate the environment (ensure the cell is moving to the correct direction)
Different types of Intermediate filaments
- cytoplasmic
- Nuclear
- include: nuclear lamin
1. include: keratin, vimentin, neurofilament
Structure of keratin
- Monomer: fibrous protein
- 2 monomer binds together will form “coiled-coil dimer”
- 2 dimer form “tetramer”
- Multi tetramer form “fibre”
Function of intermediate Filament
- Prevent rupture from mechanical stress
2.cell cohesion/adhesion
One disease from mutation in keratin
EB - epidermolysis bulloas
mutation in keratin 14
Fucntion of Nuclear Lamin and simple description of its shape
- Nuclear Lamins forms a mesh structure in the innermembrane of the nucleus
- Lamin is important to maintain the shape of nucleus
Structure of microtubule
- Monomer: tubulin
- 2 types of tubulin: alpha & beta
- alpha + beta forms protofilaments from plus end to minus end
- 3 parallel protofilaments join together to form a microtubule
plus (faster) > minus
Which tubulin is plus end ? whihc is minus end?
alpha is - end
beta is + end
Function of microtubulin
- Transpotation of organelle
- Structure support
3.cell mitosis - spindle fiber formation
The role of microtubule in cilia
major compotent in cilia : it helps cilia to move
How is microtubule regulated and 1 exmaples
through MAPS (microtubular-assocaited proteins)
Exmaples: Tau = it regulates microtubule’s stability, it may cause alzheimer’s disease)
what is Motor protein and function?
The protein that helps to move the cargo along the microtubule network
Function: important in nueorns - it helps microtubule-based axonal transportation
What is kinesin and dynein
they are both motor protein that work along microtubule to carried cargos:
1. kinesin works from + towards -
2.Dynein works from - towards +
why is dynein important in cilia
- Beating cilia on epithelia (e.g. removal of mucus)
- Cilia as signaling antennae
- Cilia in sperm motility
Dynein in the regular intervels on the microtubules → motor protein bend or move in one direction → they enable the entire microtubules to move sideway → helps things to move forward
Does kinesin and dynein need ATP?
yes
