Cell Junctions

Question 1

Epithelium

Answer 1

• tissues that line a void in the body – tend to be held tightly together by cell junctions and rest upon a basal lamina (basement membrane)
• have microvilli
• prevents things from leaking into tissues
• APICAL- top part, BASAL LAMINA- basement membrane
• things cannot move from apical to basal

Question 2

cellular junctions

Answer 2

• tight junctions tend to occur up near the microvilli surface and immediately behind those are adherence junction
  1. sealing
  2. adhesion
  3. communication

Question 3

tight junctions

Answer 3

• near top of cell, and forms seal all the way around cells
• nothing from the lumen can pass between the cells and get into the tissue or blood on the baso-lateral side
• Restricts movement within the plane of the membrane such that proteins (including channels and transporters) and phospholipids in the apical membrane domain cannot freely diffuse into the baso-lateral domain and vice versa

Question 4

adhesion junction

Answer 4

1. adherens
2. Desmisomes
3. Hemidesmisomes

Question 5

cadherin

Answer 5

holds one cell to the next, part of adhesion

Question 6

basal lamina

Answer 6

• “basement membrane” of epithelial cell

- extracelllular matrix secreted by epithelial cells

Question 7

Hemidesmisomes (bottom)

Answer 7

• adhering type of junction
• always at the bottom basal side
• instead of cadherin, it has integrins
• half a demisome, but different composition
• anchors intermediate filaments to basal lamina

Question 8

Desmosome (anywhere)t

Answer 8

• adhering type of junction
• protein plaque with cadherins (connecting proteins)
• joins intermediate filaments from one cell to another
• can be anywhere
• occur in spots

Question 9

Adherens junction (top)

Answer 9

• adhering type of junction= adhesion belt
• bundles of actin filaments, hold cell together
• cadherins- connecting proteins between cells
• at the top of cell right below tight junctions
• cancer- lose cadherin function–> cell is metastatic

Question 10

disease attacking desmosome

Answer 10

• autoimmune disease that causes blistering

- epithelial cells blister because they are not held down correctly

Question 11

gap junction

Answer 11

• plasma membrane from one cell juxtaposing plasma membrane from another cell
• allows passage of small water soluble ions
• connexin protein used to form it
• cytoplasm of one cell lines up with cytoplasm of another
• ex. found in cardiac muscle–> allows ions to flow and heart muscle gives signals through gap junctions (not nerves)
• ex. also gap junctions in inner ear–> if you have a defect, could cause deafness