Cell Adhesion and Communication Flashcards
What is epithelial tissue?
Tissue covering the surfaces of internal and external organs. All share the same basic structure: a layer of cells ontop of a basement membrane.
What type of epithelial tissue is found at alveoli?
Simple squamous epithelium
What type of epithelial tissue is found in the kidney?
Simple cuboidal epithelium
What type of epithelial tissue is found in the intestine?
Simple columnar epithelium
What type of epithelial tissue is found in the oesophagus?
Stratified squamous epithelium
What type of epithelial tissue is found in the respiratory tract?
Pseudo-stratified ciliated columnar epithelium
Name the 3 classes of cell-adhesion junctions:
- Occluding junctions
- Attachment junctions
- Communication junctions
What are occluding junctions?
Cell-adhesion junctions that form an impermeable layer between epithelial cells.
-Tight Junctions
What are attachment junctions?
Cell-adhesion junctions that link to cytoskeleton, to actin and to intermediate filaments of adjacent cells and to the extracellular matrix.
- Adherens junctions
- Desomosomes
- Hemidesmosomes
- Focal Adhesions
What are communication junctions?
Cell-adhesion junctions that directly connect cytoplasm of adjacent cells.
-Gap Junctions
Name the types of cell-cell adhesions
- Tight Junctions
- Adherence Junctions
- Desmosomes
- Gap Junctions
- Non-Junctional Adhesions
Name the types of cell-matrix adhesions.
- Hemidesmosomes
- Focal Adhesions
- Non-Junctional Adhesions
Describe the structure of occluding/tight junctions.
Bands of interconnected strands of integral membrane proteins encircling the cell. Lateral plasma membranes of cells are joined together through these sealing strands.
What are the three different types of sealing strands?
- Occludins
- Claudins
- JAMs (Junctional Adhesion Molecules)
All attach stably to numerous structural proteins to interconnect sealing strands.
What are claudins?
Core sealing strand proteins in tight junction fibrils
What are the function of claudins?
To allow passage of size/charge dependant molecules
How do claudins establish specificity?
Different claudins arrange their extracellular loops differently for different specificity pores
How many claudins have been found in humans?
24
Describe the possible effect of mutations in Claudin 16
Mutations of Claudin 16, expressed in the ascending limb of the loop of Henle, is associated with famial hypomagnesemia, hypercalciruia and nephrocalcinosis
What are the roles of Occludins and JAMs?
To provide positional stability in tight junctions
Sealing strand proteins are able to bind to signalling proteins. True or False?
True - they bind transiently.
What is paracellular transport?
Transfer of substances across an epithelium by passing through the intercellular space between the cells.
The different specificities of claudins allow tight junctions to regulate paracellular transport. True or False?
True
What is transcellular transport?
Transfer of substances across an epithelium through cells, through apical and basolateral membranes.
Describe the process of glucose absorption across intestinal epithelium.
Active process of transcellular transport uses ATP to pump Na+ out of the cell across basolateral membrane through ATPase Na+/K+ pump against concentration gradient.
Inside cell now therefore low [Na+], concentration gradient exists from apical to basolateral membrane
Glucose enters cell through Na+/Glc symporter and pass through cell down concentration gradient into bloodstream through GLUT2 transport on basolateral membrane.
Explain how apical and basolateral membranes of cells can maintain their own identity?
Tight junctions prevent diffusion of proteins and lipids between the two, maintaining the unique identity of each membrane.
In the context of glucose absorption, it is critical that the GLUT2 and Na+/K+-ATPase proteins are on the basolateral and Na+/Glc symporter on the apical.