Gap Junctions

Question 1

Tight Junctions

Answer 1

• Web-like strands of transmembrane proteins
• Fuse adjacent plasma membrane outer surfaces together
• prevents any passage of substances
• Run around the whole circumference of the cell
• Often found in Epithelial tissue

Question 2

Adherens Junctions

Answer 2

• Forms Adhesion Belts, Runs around the circumference of the cell
• Helps to resist separation during various activities
• Cadherins (Transmembrane Glycoproteins) insert into the Plaque (Dense layer of proteins) from the opposite side of the plasma membrane, crosses the intercellular space and connects to other Cadherins in the adjacent cell

Question 3

Desmosomes

Answer 3

Similar to Adherens, with Cadherins which connect adjacent cells, however the Plaque isn’t attached to the Microfilaments, instead it connects to Intermediate filaments on the Cytoskeleton, which contain Keratin. The Immediate filaments connect from one side of the cell, across the Cytosol, to Desmosomes on the opposite side fo the cell

• common amount cells that make the epidermis layer of skin
• Prevents cells separating under tension

Question 4

Hemidesmosomes

Answer 4

• Resemble Desmosomes, however they don’t link adjacent cells
• Transmembrane Glycoproteins are integrals, not Cadherins. Inside the plasma membrane, Integrins attach to intermediate filaments (Made of Keratin)
• On the outside of the cell, these filaments attach to Laminin, a protein found on the Basement membrane
• Hemidesmosomes anchor themselves to the basement membrane

Question 5

Gap Junctions

Answer 5

Membrane proteins, Connexins, form tiny fluid-filled tunnels called Connexons, connecting neighbouring cells, however the plasma membrane is not fused together, but are separated by narrow intercellular gaps, allowing small molecules and ions to diffuse through - allowing cells to communicate with one another (Nerve impulses)