Membrane Proteins & Cell Junctions

What are the two main types of membrane proteins?

1. Integral (intrinsic)

2. Peripheral (extrinsic)

Integral membrane proteins:

Amphipathic proteins inserted into the lipid bilayer, sometimes spanning the membrane (transmembrane)

What are peripheral proteins?

Proteins attached to the membrane surface; not amphipathic and do not penetrate the bilayer

What are glycoproteins

Proteins with attached carbohydrates that face the extracellular space; form part of the glycoalyx

What are desmosomes

Adhering junctions anchoring cells together in tissues subject to mechanical stress (eg heart muscle)

What are the main structural proteins in desmosomes

1. Plaques (anchor site)

2. Cadherins (link cells)

3. Intermediate filaments (structural support)

What are tight junctions and their main protein component?

Impermeable junctions formed by occluding that prevent paracellular movement of molecules

What are the key functions of tight junctions?

Limit movement between cells, force molecules through cells, and prevent membrain protein migration

What are gap junctions?

Communications junctions made of connexons that link cytoplasms of adjacent cells for electrical and metabolic coupling

What do connexons do

Form channels allowing passage of ions and small molecules between cells