Intercellular Junctions

Question 1

How do neighbouring cells communicate?

Answer 1

Neighbouring cells adhere, interact (transfer substances) and communicate via channels or pores in the plasma membrane.

Question 2

Cell surface ______ allows the transfer of substances to external environment to occur.

Answer 2

modification

Question 3

3 types of cellular junctions:

Answer 3

> Desmosomes
Gap junctions
Tight junctions

Question 4

What are desmosomes? (2)

Answer 4

• Cell membranes separated but held together by complex keratin proteins that extend from a disc in the cytoplasm (of both neighbouring cells) through their membranes and across the space between the cells.
• Whole structure anchored by intermediate filaments inside each of the cells.

Question 5

What are the functions of desmosomes?

Answer 5

Anchoring junctions, i.e. holds cells firmly together into strong sheets, e.g. muscle cells

Question 6

What are gap junctions?

Answer 6

As in desmosomes, but the connection protein (connexion) is organised into regulated channels between the two cells.

Question 7

What is the function of gap junctions? (2)

Answer 7

• Function: allow for the direct transport of small molecules from one cell to the next
o Polar molecules that are hydrophilic are able to move through
o Ions, sugars and amino acids etc.

Question 8

What are tight junctions?

Answer 8

• Membranes held together tightly by integral proteins that are common to both membranes.

Question 9

What are the functions of tight junctions?

Answer 9

• Functions: to seal off environments on either side of a cell layer and restrict movement to transmembranal only, e.g. tight junctions between skin cells prevent leakage between cells in sweat glands