Cell Junctions and Surface Specializations

Question 1

What are cadherins?

Answer 1

Class of Proteins
Attach one cell to another by binding to other cadherins
Stabilized by the actin cytoskeleton of the cell.

Question 2

What proteins link cadherins to the cells actin cytoskeleton?

Answer 2

Catenins

Question 3

Function of cadherins and selectins is dependent on what molecule?

Answer 3

Ca+2

Question 4

What do selectin proteins bind to?

Answer 4

Carbohydrates

Question 5

Why are selectins integral to the inflammatory response?

Answer 5

They are important for controlling movement of leukocytes from blood into tissues.

Question 6

Integrins?

Answer 6

Integral membrane proteins that will link to actin

Heterodimer - unique combination of alpha and beta chains

Question 7

What do integrins bind to?

Answer 7

Inside cell - cytoskeletal actin

Outside cell - Tripeptide RGD (arg-gly-asp) on ligands (laminin, fibronectin, tenascin, vitronectin, collagen..)

Question 8

CAM?

Answer 8

Cell adhesion molecule

Question 9

Occluding (tight) junctions

Answer 9

Define cell polarity

prevent anything from slipping between cells

Question 10

Zonula adherens (belt desmosome)

Answer 10

Associated with actin filiaments

beltlike distribution

Question 11

Macula adherens (spot desmosome)

Answer 11

Associated with intermediate filaments
Stronger attachement than belt desmosome.
Like a “spot weld”

Question 12

Hemidesmosome

Answer 12

Link the basal domain of an epithelial cell to the basal lamina
Intermediate filaments are associated with a plaque

Question 13

Gap junctions

Answer 13

Allow cells to communicate with each other chemically and elctrostatically

Question 14

What are gap junctions formed by?

Answer 14

Connexons - channel like structures that enable the passage of small molecules between cells.
Comprised of six integral membrane proteins called connexins

Question 15

What is the usual order of the five anchoring junctions from top to bottom?

Answer 15

Occluding junction
Zonula adherens (belt desmosomes)
Macula adherens (spot desmosomes)
Gap junctions
Hemidesmosomes

Question 16

What type of problems are usually associated with connexin mutations?

Answer 16

Nervous system problems

Question 17

Microvilli purpose?

Answer 17

Increase cell surface area

Question 18

Cilia purpose?

Answer 18

Motion/Movement

Question 19

What is the terminal web?

Answer 19

A horizontal of actin filaments that links that actin cores of microvilli

Question 20

What cytoskeleton filaments are cilia and flagella made of?

Answer 20

Microtubules

Question 21

What provides the force for cilia movement?

Answer 21

Dyneins

Question 22

Where do cilia develop from?

Answer 22

Basal bodies - derived from centrioles, rootlets anchor these structures to the cytoplasm

Question 23

What are the 2 proteins involved in an occluding junction?

Answer 23

Occludin and claudin

Question 24

Zonula Adherens (belt desmosomes) are constructed by what two proteins?

Answer 24

Cadherins and catenins

Question 25

What is Leucocyte adhesion deficiency type 1 (LAD-1)?

Answer 25

Absence of mutations of beta 2 integrins