Cell - cell interactions

Question 1

4 major cell junctions

Answer 1

1. occluding junctions - tight junctions
2. anchoring junctions - adherens junctions
3. communicating junctions - gap junctions
4. desmosomes
   p/s; mutations in gap junctions cause white matter degeneration (Pelizaeus-Merzbacher disease & multiple sclerosis)

Question 2

Occluding junction functions

Answer 2

• seal cells in an epithelial sheet
• block flow of fluids between epithelial cells
• prevent movement of integral membrane protein between apcal and basolateral membrane
• epithelial cells in lung - if injured result in lung disorder (autocrine stimulation)

Question 3

Adhesive junctions

Answer 3

1. mechanical attachment to one another
2. keep cardiac muscles together when expand and contract
3. keep epithelial cells tgt
4. contact inhibition - stop cells growth when they touch each other
5. build from - cadherins and catenins

Question 4

Communicating junctions - gap junction

Answer 4

1. communicating - allow direct passage of chemical/electrical signals from cell to cell
2. passage of ions and small molecules - muscle

Question 5

desmosomes

Answer 5

• adhesive
• physically joints cells together at discrete point
• tissues eg. skin
• provide connections between intermediate filaments of cell cytoskeleton

Question 6

plasmodesmata

Answer 6

• communicating
• ease connection between plant cells (enable plants transmit signals)
• sheated by plasma membrane