Cytoskeleton

Question 1

What are the three main types of intercellular interaction?

Answer 1

1. Occluding junctions: seal cells tightly together to prevent the passage of any small molecules (ie epithelial cells)
2. Anchoring junctions: mechanically attached cells to each other or to the shared ECM using actin or intermediate filaments between cells for attachment
3. Communication junctions: gaps between cells which mediate the transfer of chemicals or electrical signals between interacting cells

Question 2

What are 3 examples of communicating junctions?

Answer 2

Gap junctions; chemical synapses; plasmodesmata (plants only)

Question 3

What are two types of anchoring junctions?

Answer 3

Desmosones and hemidesmosomes

Question 4

How do desmosomes and hemidesmosomes relate to junctions?

Answer 4

Both are types of cell-anchoring junctions.

The first holds cells together at adherens junctions using attractive and adhesive transmembrane proteins called adherens

The latter involves focal adhesions, or the binding of cells to the ECM using transmembrane proteins called integrins

Question 5

What do occluding junctions primarily form?

Answer 5

These junctions primarily form selective permeability barriers between cells and their surrounds, so that molecules can be transferred against their concentration gradients

Question 6

Describe the structure of a tight, or occluding, cell junction.

Answer 6

This type of cell junction is composed of a row of opposing transmembrane adhesion proteins called claudins and occludins

Question 7

What is the role of claudin transmembrane proteins in occluding, or tight, junctions?

Answer 7

Specific claudins allow the passage of specific solutes through the tight, or occluding, cellular junctions; claudins facilitate the selectivity/specificity of molecular passage through tight cellular junctions

Question 8

What are the 3 main components of the cytoskeleton?

Answer 8

1. Actin
2. Microtubules
3. Filaments

Question 9

Define the cytoskeleton.

Answer 9

An interconnected system of bundled fibers, slender threads, and lattices that extend from the nucleus to plasma membrane

Question 10

What are the monomer units of microfilaments?

Answer 10

Actin monomers are subunits of…

Question 11

What are the monomer units of intermediate filaments?

Answer 11

Fibrous subunits are monomers of…

Question 12

What are the monomer units of microtubules?

Answer 12

Tubulin dimers are monomers of…

Question 13

From which structure do microtubules grow?

Answer 13

The centrisome!

Question 14

True or false: Microtubules can be modified post-translation

Answer 14

True; microtubules can be modified post-translation by tyrosination, acetylation, phosphorylation, polyglutamylation or polygycyation