Centrioles, Cilia, and Cell Junctions Flashcards
(37 cards)
How do animals maintain their shape in the cytoplasm?
Cytoskeleton
What does the cytoskeleton consist of?
System of tubular and filamentous structures
List three elements that make up the cytoskeleton system
Microtubules, Microfilaments, and Intermediate Filaments
What is the thickest filament?
Microtubule
Describe the appearance of a microtubule
Rigid in structure, hollow cylinders, composed of 13 subunits
Discuss the heterodimer present in the subunits
Two proteins: a-tubulin and b-tubulin
Discuss the structural and functional role of microtubules
They form the axoneme (central core) of the cilium and flagellum which are important in cell movement.
They form the components of the centrioles.
They also form the spindle fibres of cell division
Associated with intracellular movement in the axons of nerve cells.
Solid filaments are also known as…
Apart from microtubules more solid filaments called microfilaments (= actin filaments) may be seen under high EM magnifications.
These are solid filaments, 5-6 nm diameter.
What are microfilaments made of?
Protein actin
Where are microfilaments found?
Cell cortex (below plasma membrane)
What can microfilaments produce?
Intestinal microvilli
How do microfilaments generate movement?
Rapidly assembling and disassembling
Which filament is being discussed here? Heterogeneous in composition
Any given cell will have more than one type
One type of filament usually predominates
Intermediate filaments
List and describe the four main types of intermediate filaments
Type I - keratins divided into acidic and basic types
Type II - vimentin-like proteins, found in cells of mesodermal origin
Type III - neurofilaments, found in nerve axons
Type V - nuclear lamins - forming the nuclear lamina
What’s the basic building block of an intermediate filament?
Dimer, formed through interaction of the rod domain to form a coiled coil.
Describe centrioles
Usually found as two cylindrical structures at right angles to one another.
Typically one pair per cell during interphase
Usually found in cytoplasm in an area near the nucleus.
Often associated with Golgi apparatus.
What is the area where centrioles are found?
Microtubular organizing center.
Describe the composition of a centriole
Composed of 9 sets of ‘triplets’ arranged as a cylinder.
Called a 9x3 structure (or 9+0 structure).
Each set is a triplet of associated microtubular elements.
Consist of protein tubulin.
What is the cartwheel in a centriole?
Additional material that protrude from the outer surface at proximal end of a mature centriole.
Fibrous structures connecting the two centriole cylinders.
What happens to centrioles prior to cell division?
Prior to cell division the centrioles replicate and move to the opposite poles of the cell.
Most cells’ centrioles duplicate by the growth of new daughter centriole at right angles to the ‘old’ centriole.
One new centriole and one old centriole.
Form areas known as centrosomes (‘mitotic centre’)
What is the centrosome also known as?
The main microtubule organizing centre (MTOC) of the cell.
What are centrosomes composed of?
Two orthogonally (right angle to each other) arranged centrioles
Pericentriolar material.
Contains proteins responsible for microtubule nucleation and anchoring.
Where do microtubules come from?
Instead, microtubules originate from y-tubulin rings in the centrosomal matrix (Distal appendages) not from the centrioles.
Each y-tubulin ring serves as the nucleation site (starting point) for one microtubule.
What do asters of microtubules form?
Visible spindle fibres of cell division
Some spindle fibres bind to the chromosomes at the centromere.
