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FUNBIO - SNQ > Centrioles, Cilia, and Cell Junctions > Flashcards

Centrioles, Cilia, and Cell Junctions Flashcards

1
Q

How do animals maintain their shape in the cytoplasm?

A

Cytoskeleton

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2
Q

What does the cytoskeleton consist of?

A

System of tubular and filamentous structures

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3
Q

List three elements that make up the cytoskeleton system

A

Microtubules, Microfilaments, and Intermediate Filaments

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4
Q

What is the thickest filament?

A

Microtubule

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5
Q

Describe the appearance of a microtubule

A

Rigid in structure, hollow cylinders, composed of 13 subunits

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6
Q

Discuss the heterodimer present in the subunits

A

Two proteins: a-tubulin and b-tubulin

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7
Q

Discuss the structural and functional role of microtubules

A

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.

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8
Q

Solid filaments are also known as…

A

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.

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9
Q

What are microfilaments made of?

A

Protein actin

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10
Q

Where are microfilaments found?

A

Cell cortex (below plasma membrane)

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11
Q

What can microfilaments produce?

A

Intestinal microvilli

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12
Q

How do microfilaments generate movement?

A

Rapidly assembling and disassembling

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13
Q

Which filament is being discussed here? Heterogeneous in composition
Any given cell will have more than one type
One type of filament usually predominates

A

Intermediate filaments

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14
Q

List and describe the four main types of intermediate filaments

A

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

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15
Q

What’s the basic building block of an intermediate filament?

A

Dimer, formed through interaction of the rod domain to form a coiled coil.

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16
Q

Describe centrioles

A

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.

17
Q

What is the area where centrioles are found?

A

Microtubular organizing center.

18
Q

Describe the composition of a centriole

A

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.

19
Q

What is the cartwheel in a centriole?

A

Additional material that protrude from the outer surface at proximal end of a mature centriole.
Fibrous structures connecting the two centriole cylinders.

20
Q

What happens to centrioles prior to cell division?

A

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’)

21
Q

What is the centrosome also known as?

A

The main microtubule organizing centre (MTOC) of the cell.

22
Q

What are centrosomes composed of?

A

Two orthogonally (right angle to each other) arranged centrioles
Pericentriolar material.
Contains proteins responsible for microtubule nucleation and anchoring.

23
Q

Where do microtubules come from?

A

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.

24
Q

What do asters of microtubules form?

A

Visible spindle fibres of cell division

Some spindle fibres bind to the chromosomes at the centromere.

25
Q

What do intercellular junctions allow?

A

These junctions may allow cells to form strong interconnections with one another, prevent the passage of materials, or establish rapid junctions.

26
Q

What are the three types of junctions?

A

There are 3 types of cell junction:
Adhering (Adhesion or
Anchoring) Junctions
Tight Junctions
Gap Junctions

(plant cells are connected by plasmodesmata)

27
Q

What is an adhering junction?

A

Strong junctions that tightly bind adjacent cells, such as those found in outer layer of mammalian skin.

28
Q

What is the role of a cadherin?

A

Act as important components for anchoring cells together. Cadherins form links to cytoplasmic structures
Links membrane to cytoskeleton.

29
Q

Adherens Junctions is defined as a cell junction whose cytoplasmic face is…

A

…linked to theactin cytoskeleton.

30
Q

How are caherins attached in adherens junctions?

A

The cadherin attachment is via linker proteins to actin microfilaments in the cytoplasm.

31
Q

Explain the differences between spot and hemi desmosomes

A

Macula adherens or spot desmosomes:

Like a spot rivet
Connect cells to each other by transmembrane linker proteins (cadherins, desmogleins).
Contribute to tissue stability e.g. between muscle cells of heart.

Hemidesmosomes (i.e. half a desmosome) :

Connect the basal surface of epithelial cells to the underlying basal lamina.
The transmembrane linker proteins here are different - integrins.
Help resist frictional or abrasive forces (e.g. epithelial tissues).

32
Q

What type of movement is seen within a gap junction?

A

Involved in the movement of small inorganic ions and molecules between adjacent cells.

33
Q

What transmembrane proteins make up a gap junction?

A

Connexins

34
Q

What do the aligned arrays result in when talking about gap junctions?

A

This results in the formation of a hydrophilic channel with a pore size of about 1.5nm diameter.

35
Q

What are tight junctions?

A

These appear as a fusion of the plasma membranes of two cells.
These are called tight junctions or zonula occludens.

36
Q

What’s the function of tight junctions?

A

Function is to seal off the intercellular space, forming almost impermeable barrier. Have a role in the maintenance of concentration gradients between the exterior lumen and the intercellular space.

37
Q

What happens to desmosomes during pemphigus vulgaris?

A

Autoantibodies target proteins of the desmosome leading to disruption of cell adhesion.

FUNBIO - SNQ (3 decks)

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