BIO 2 EXAM 1 Cell Junctions Flashcards
5 types of cell junctions…
Adherens Junctions
Desmosomes
Hemidesmosomes
Tight Junctions
Gap Junctions
Defining Adherens Junction…
Allows for cell-cell adhesion
A continuous zone or belt around the cell near the apical side
Connects to actin microfilaments
Cadherins are integral membrane proteins
bind a Ca2+ ion
bind another Cadherin
Connect to bundled actin filaments
Defining Desmosomes…
“-some” = body
Also used for cell-cell adhesion
Single point (not a zone or a belt)
Also uses Cadherins
Connects to Intermediate Filaments
Defining Cell-to-Cell adhesion
Adherens Junction and Desmosomes
Cytoskeletons are connected across the entire tissue
Defining Hemidesmosomes…
Cell-basal lamina adhesion
Single point of attachment
Connects to Intermediate Filaments
Different transmembrane protein: Integrin
Many different Integrin proteins
Heterodimer of one a subunit and one b subunit
The extracellular domain binds basal lamina proteins
The transmembrane domain of one a helix
Intracellular domain binds IFs
Defining Tight Junctions…
Not for adhesion
Makes a waterproof seal between two cells
Continuous zone
Apical to the Adherens junction
Multiple lines of connecting proteins
Claudins are the major transmembrane protein
Neighboring claudins are tightlypacked to make waterproof seal
Defining Tight Junction domains…
creates two membrane domains!
Apical and Basal (or basolateral)
Proteins can move freely within either domain
Cannot cross the claudins to get from one domain to the other
Defining Gap Junctions…
Single spot
Cell-cell communication
Six Connexin proteins on each cell
The aqueous channel between cells allows any molecule up to ~1200 molecular mass
Cytosol is continuous within theepithelial tissue
