Cell Junctions -Week 11

Question 1

name the main types of cell junctions and name the proteins that make up each

Answer 1

• Anchoring junctions- transmembrane adhesion proteins of the integrin family
• Tight junctions- Claudin & Occludin proteins
• Gap junctions- proteins call connexins

Question 2

For tight junctions: describe the arrangement of tight junctions between cells in an epithelial sheet

Answer 2

the junctions are made up of transmembranous proteins/glycoproteins, the claudin protein on one cell will bind to another claudin protein on the other cell, this also happens to occludin proteins
this seals the passage of substance so no small molecules leak out

Question 3

Which of the following can pass through gap junctions?

1.Proteins
2.Ions
3.mRNA
4.Metabolites (e.g. sugars, amino acids)
5.Secondary messenges such as cyclic (c)AMP

Answer 3

2, 4 & 5

Question 4

what are the 3 main roles of Tight junctions

Answer 4

1) Holds cells together
2) prevents passage of molecules between cells (acts as a selective filter as it forces molecules to go through the epithelial cell)
3) Block movement of membrane proteins between regions of cells- allowing specialised cells to do specific functions