Epithelial Cell Specializations

Question 1

Explain the concept of epithelial cell polarity

Answer 1

-Position of organelles
-apical surface characteristics
-cell to cell junctions
-cell basement membrane junctions

Question 2

What specializations occur on the apical surface? (5)

Answer 2

1. Microvilli
   2.Cilia (motile)
2. Primary Cilia (non motile)
3. Sterocilia
   5.Glycocalyx

Question 3

What are the specializations on the lateral surface? (4)

Answer 3

Zonula occludens
Zonula adherens
Macula adherens (Desmosomes)
Macula communicans (Gap junctions)

Question 4

Although not usually visible on light microscopy, what specialization can be seen as a brush border? what surface is this a specialization?

Answer 4

Microvilli, apical

Question 5

What filament supports microvilli?

Answer 5

actin which connects to the terminal web

Question 6

Define glycocalyx

Answer 6

gelatinous glycoprotein-polysaccharide covering the cell membrane of some epithelia

Question 7

Which stain would give you clear identification of the glycocalyx? and why?

Answer 7

PAS, because it targets the carbohydrates in the glycoproteins

Question 8

What filament supports Cilia?

Answer 8

microtubules which are connect to basal bodies

Question 9

What motor protein is supportive of microvilli?

Answer 9

Myosin

Question 10

What motor protein is supportive of motile cilia?

Answer 10

Dynein

Question 11

What is the main difference between motile cilia and non motile primary cilia?

Answer 11

The configuration of the microtubules, primary cilia lack the doublet as well as the dynein proteins

Question 12

What filament supports stereocilia?

Answer 12

Actin

Question 13

What physical characteristics differentiate sterocilia from motile and non motile cilia?

Answer 13

the length, the actin core, and the connections to adjacent stereocilia

Question 14

Define zonula occludens

Answer 14

-first junction on the lateral surface
- provides selectively permeable barrier

Question 15

What are the adhesive proteins and cytoskeleton protein of zonula occludens?

Answer 15

Occluden
Claudin

Actin

Question 16

Define zonula adherens

Answer 16

-beneath zonula occludens
-mainly responsible for adhesion between cells

Question 17

What protein forms the intercellular junction of zonula adherins? what is the cytoskeleton protein?

Answer 17

E-cadherin

Actin

Question 18

What adhesive components and filament supports desmosomes (macula adherens)?

Answer 18

Desmoglein
Desmocollin

Intermediate filaments

Question 19

What lateral surface specialization is integral to cell-cell bond strength?

Answer 19

Desmosomes (macula adherens)

Question 20

What proteins comprise Gap Junctions (macula communicans)?

Answer 20

Connexins and connexons

Question 21

What are the roles of the basement membrane (basal lamina)?

Answer 21

-Physical support
-Guide for cell adhesion and migration
- Cell signaling

Question 22

What are the components of the basement membrane?

Answer 22

-Collagen (type IV)
-Glycoproteins
-Proteoglycans

Question 23

What stain could you use to highlight the collagen in the basement membrane?

Answer 23

Silver

Question 24

What is the purpose of basal infold and outfolds?

Answer 24

• Increase surface area for molecular transport
  -Increase surface area for attachment