Lecture 6 Flashcards
Original views on cell structure
scientists thought that organelle floated freely in the cytoplasm of a cell
eventually improvements in both light and electron microscopy revealed that the cell contained a cytoskeleton
cytoskeleton
extends throughout the cell
acts like a dome tent stabilised by opposing forces
but its also very dynamic and can be dismantled and reassembled quickly to change the shape of the cell
the cytoskeleton definition
a network of fibres extending throughout the cytoplasm
roles of the cytoskeleton
support, mobility, divison and regulation
it organise the cell structures and activities anchoring many organelles and can be quickly dismantled and rebuilt
extends throughout the cytoplasm providing mechanical support and to maintain cell shape
organises cell structures and activities
three types of molecular structure in cytoskeleton
microtubules
actin filaments
intermediate filaments
Cytoskeleton- it interacts with motor proteins to produce mobility
inside the cell, vesicles can travel along monorails provided by the cytoskeleton
Cytoskeleton- Movement of vesicles within the cells
vesicles of proteins that leave the ER and move to the Golgi and transported along cytoskeletal tracks
the cytoskeleton also manipulates the plasma membrane making it bend inward to form food vacuoles or phagocytic vesicles
Microtubules
are the thickest of the three fibres
maintenance of cell shape, cell motility and organelle movements
made up of tubulin
Actin filaments
are the thinnest
maintenance of cell shape
muscle contraction
cell division
Intermediate filaments
are fibres with diameters in a middle range
maintenance of cell shape
anchorage of nucleus and other organelle
Microtubule functions
organising role
grow out from a centrosome
providing a system of tracks along which other organelles and vesicles are moved
also responsible for anchoring organelles within the cells
form mitotic spindle
also present in cilia and flagella
Centrosomes and centrioles
in many cells, microtubules grow out from a centrosome near the nucleus
the centrosome is a microtubule-organising centre
in animal cells, the centrosome has a pair of centrioles each with nine triplets of microtubules arranged in a ring
Centrosome
a region near the nucleus where the cells microtubules are initiated
each includes a pair of centrioles at right angles to each other
metaphase
condensed chromatin
mitotic spindle is made of tubulin
mitotic spindle radiated out from the centrosome
chromosomes bind to spindle via kinetochores
the kinetochore is bound to centromeric DNA
Cillia and flagella
Microtubules control the beating of cilia and flagella
they differ in their beating patterns
cilia can be found on the surface of a cell and can move liquid along
flagella moves cells forward in one direction
Ultrastructure in cilia and flagella
a core of microtubules heated by the plasma membrane
a basal body that anchors the cilium or flagellum
a motor protein called dyne which drives the bending movement of a cilium or flagellum
microtubules as targets for anti-cancer drugs
they inhibit mitotic spindle formation which prevents cell division and causes death in these cells
Actin filaments
two intertwined strands of actin n
made up of actin
maintenance of cell shape and changing cell shape
muscle contraction
cell motility and division
Cortex
a 3D network of microfilaments
Microfilaments
contain myosin and actin
in muscle cells thousand of actin filaments are arranges parallel to one another
thicker filaments composed of myosin interdigitate with the thinner actin fibres
Blebbing
dissociation of plasma membrane from actin cytoskeleton
Cytoplasmic streaming
is a circular flow of cytoplasm within cells
a way of stirring up the contents of the cytoplasm
intermediate filaments
fibrous proteins supercoiled into thicker cables
one of several different proteins of the keratin family
maintenance of cell shape
anchorage of nucleus and other organelle
formation of nuclear lamina
What is the most durable of the 3 filaments
intermediate filaments
