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Lecture 2

BIOL 130 Lecture 2: Unit 10 Cytoskeleton

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University of Waterloo
BIOL 130
Heidi Engelhardt

Unit 10 Cytoskeleton Types of cytoskeletal filaments • Network of fibres forming scaffolding within Microtubules cytoplasm • Biggest, thickest – largest diameter o Temporary material built at the sides so that • Radiate out to edges of cell from an organizing materials can be moved centre close to nucleus/ centre o Temporary – can be taken down and shifted • Stiff hollow tubule – drinking straw – not rope • Determine cell shape – makes cell look the way it • Organizing roles does o Anchor organelles in place - Grow from • Allows the cell to function like it does structure and decide where organelles will be. • Position and movement of organelles/ components Eg. RER, nucleus - where nucleus is, arrangement of ER and Golgi, o System of track created by the microtubules movement of vesicles – cytoskeleton provides that allow cargo to be moved in cell - Vesicles system of movement cross to other organelles on microtubule tracks o Coordinates movement of chromosomes o Reorganize themselves during mitosis to form during mitosis mitotic spindle • Allows movement – motility o Form stable structure on certain cells – cilia, o Forms flagella, cilia, lamellipodia flagella • Cytoskeleton is dynamic – constantly being • Microtubule organizing centres o Structures from which microtubules originate reorganized o Serves as both ‘bones’ and muscles of the cell and radiate outward o Ex. Centrosome (2 centrioles) Prokaryotes and cytoskeletons ▪ Role unclear – organization of mitotic/ • Once thought to be a feature of eukaryotes only meiotic spindle apparatus • Recent advances in microscopy have shown tht o Basal body – at base of cilia/ flagella prokaryotes do have some organization – ex. Binary fission – move chromosomes o Found tht there are comparable elements of cytoskeleton in prokaryotes that play similar roles as in eukaryotes Cross section of intestinal mucosa • Microtubules – hollow tubes of protein called Tubulin o consists of tubulin (α + β) ▪ bound to each other tightly (non-covalently) ▪ dimers polymerize to form walls of hollow 1. Epithelium tissue tube ▪ always – α binding to β 2. Connective tissue o protofilaments have structural polarity 3. Muscle tissue 4. Neural tissue ▪ α exposed at one end, β at the other ▪ all protofilaments • Tight junctions – sealing certain proteins above and oriented same way, so bellow the junction entire tubule has polarity • Basal layer – basement ▪ aligned to form cylinder membrane ▪ one end is easier to polymerize to – called + end, - end anchored in the organizing centres o dynamic, growing and shrinking as subunits are o Muscle contraction, vesicle and organelle transport, cell motility, cytokinesis added or removed ▪ dimers will add spontaneously, especially to o Originally discovered in muscle cells – now ‘plus’ end known to be in all eukaryotic cells o if nothing is there to influence o Kinesins – move vesicles toward plus end ▪ Move from ER to Golgi to plasma the + end, microtubules will grow and shrink continuously membrane o capping proteins that interact ▪ large protein superfamily, globular ‘motor’ with the tubules stabilize domain is common element o Dyneins – move toward minus end microtubules ▪ Move from plasma membrane to golgi ect. o Expanding cell with nucleus at bottom ▪ include motor proteins that drive movement of cilia and flagella  much faster than kinesin motors o Reticulum – net – microtubules dictate where the ER is o Mitosis run by spindle fibres – to stop mitosis – add spindle poison – tht interferes with tubulin polymerization ▪ Drugs tht affect microtubules • Taxol – binds and stabilize microtubules • Colchicine, Colcemid, Vinblastine, vincristine – binds tubulin dimers and prevents their polymerization ▪ Globular heads have an ATPase domain – where they remove phosphates – that ᵜ Antimitotic – chemotherapy for cancer tht makes an interaction on the α,β tract that stops, tubulin polyermizaton/ they move on uncontrolled division ᵜ Also used for karyotyping • The globular head will interact with either α or β only ▪ The track is very busy – kinesins and dynein • Motor proteins moving at the same time o Microtubules (monorail type tracks in the cells) form rails- Motor protein provide engine (power train cars that allow stuff to be moved • Cillia and Flagella contain stable microtubules o Still using tubulin – still joining tubulin the through the cell) protofilament – does not form drinking straw – ▪ These stuff could be vesicles that have been budded off forms hairs – doublets – highly conserved • Neuron – an extreme example across all eukaryotes o Protozoan flagellum and sperm flagellum = o Neurons are extremely long – they are same specialized secretory cells o Ciliated paramecium and cilia in lungs = same o Vesicles from the cell body where proteins are synthesized must travel to the axon terminal to o Interacting b/w these proto-filaments are motor proteins – use dynein and kinesin be exocytosed. o Microtubules assist in moving these vesicles from cell body to axon terminal. • Motor proteins – class of biological motors that move things along o powered by hydrolysis of ATP- taking off the terminal phosphate (they are AT
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