What is a membrane Flashcards
phospholipid head
negatively charged
polar
hydrophilic
tail
uncharged
non polar
hydrophobic
is the phospholipid bilayer fluid or rigid
fluid
what can ccross the bilayer
O2, CO2, NH3 and water itself
what cant cross bilayer
ions, proteins, and sugars are insoluble in the hydrophobic membrane core
peripheral membrane proteins
Not embedded within the membrane
Instead they adhere tightly to the cytoplasmic or extracellular surfaces of the PM
integral proteins
Some proteins span the lipid bilayer once or several times – transmembrane proteins
Some are embedded but do not cross the bilayer
Some are linked to a lipid component of the membrane or a fatty-acid derivative that intercalates into the membrane (see next slide)
Pores and channels
Serve as conduits that allow water or specific ions to flow passively through the lipid bilayer
carriers
Either facilitate the transport of a specific molecule or couple the transport of a molecule to that of other solutes
pumps
Use energy that is released through the hydrolysis of ATP to drive the transport of substances into or out of cells against energy gradients
docking marker acceptors
Located on the inner membrane surface
Interact with secretory vesicles leading to exocytosis of the vesicle contents
glycocalyx
layer formed by glycoproteins and glycolipids
tight junctions
Join the lateral edges of epithelial cells near their lumenal (apical) membranes. (tight or leaky)
links adjacent cells to prevent diffusion
desmosomes
Adhering junctions that anchor cells together, especially in tissues subject to stretching. (e.g. skin, heart, uterus)
provide mechanical strength
gap junctions
Communicating’ junctions that allow the movement of charge carrying ions and small molecules between two adjacent cells.
