A biological membrane that separates the interior of all cells from their outside environment

It is selectively permeable to ions & organice molecuels and controls the movement of substances inand out of cells.

It consists of the lipid bilayer embedded with proteins.

site of protein synthesis, protein folding, UPR, ERAD, Ca storage (SER)

rough e.r.: synthesizes proteins

smooth e.r.: synthesizes lipids, steroids, and morphine

A protein that is permenantely attached to a plasma membrane.

• Most integrins are transmebrane proteins but not all
• All have hydrophobic and heydrophilic area.
• These proteins are mainly involved in transport as channels, carriers, or receptors.

Membrane proteins that imbed only TEMPORARILY to the biological membranes they are associated with. Unlike integral proteins, peripheral ones attach loosesly and are easily removed. 

They can serve to help support the membrane on the cytoplasmic side or serve mechanical functions.

• intercellular adhesion: "adheadion between cells". The adhesion of mebrane proteins of adjacent cells
• cell-cell recognition: The process of glycoproteins on cells serving as identification tags for other cells
• attachment to the cytoskeleton and extracellular matrix: When membrane proteins serve as an attachment site for elements of the cell's cytoskeleton  and for the extracellular aamtrix. This helps maintain cell shape and fix the location of certain membrane proteins

"Impermeable" junctions caused by the fusion of adjacent cells by interlocking junctional proteins

• These junctions prevent molecules from passing through the itnercellular spaces, the "impermeable" junction encircles the cell.
• I.e. Most minerals absorbed are transferred through the tighet junction of intestinal cells.

• A type of anchoring junction that bind adjacent cells
• Help to resist pulling forces.
• Desmosomes are randomly arranged on the lateral sides of plasma membranes
• Help to form an internal tensin-reducing network of fibers.

A type of nexus junciton that directly connects the cytoplasm of two cells through channels.

• It allows chemical substances to pass freely from one cells to the next for intercellular communciation

A disorder of or that impacts the gastrointestinal track.

The disease leads to increased gut permeability due to damage associated with diseases (ulcers, inflammation) that make the gut "leaky".

• Results in insufficeient activity of an lysosomal enzyme (hexosaminidase A, that catalyzes the biodegration of lipids.
• A loss-of-function disease often due to a mutation of a protein that inpacts:
• balance in proteinfolding
• protein trafficking
• protein degradation
• an alter in protein homeostasis