The addition of the 3’-CCA is catalyzed by the enzyme tRNA nucleotidyltransferase, which functions as a nontemplate-directed RNA polymerase.

TLS Online TPP Program

#Id: 1447

#Unit 4. Cell Communication and Cell Signaling

Tight junctions prevent the diffusion of: 

Macromolecules

Small water-soluble molecules

Ions

Membrane proteins 

Glycolipids

TLS Online TPP Program

#Id: 1448

#Unit 4. Cell Communication and Cell Signaling

Ca2+-dependent cadherin- mediated adhesion also plays an important role in tight-junction formation, stability, and function.

TLS Online TPP Program

#Id: 1449

#Unit 4. Cell Communication and Cell Signaling

Gap junctions permit the passage of molecules as large as 1.2 nm in diameter (molecules smaller than 1200 Da).

TLS Online TPP Program

#Id: 1450

#Unit 4. Cell Communication and Cell Signaling

Ions, low-MW precursors of cellular macromolecules, products of intermediary metabolism, & small intracellular signaling molecules can pass from cell to cell through gap junctions.

TLS Online TPP Program

#Id: 1451

#Unit 4. Cell Communication and Cell Signaling

Cell-adhesion molecules (CAMs) mediate direct cell-cell adhesions.

TLS Online TPP Program

#Id: 1452

#Unit 4. Cell Communication and Cell Signaling

Adhesion receptors mediate cell-matrix adhesions.