lecture 1 Flashcards
what are multicellular organisms composed of
many different cell types
animal cell specific
extracellular matrix: specialized material outside of the cell
lysosome: degradation of cellular components that are no longer needed
plant cell specific
cell wall: cell shape and protection against mechanical stress
vacuoles: degradation and storage
chloroplasts: site of photosynthesis
membrane bilayers
two layers or leaflets of lipid molecules
what is a lipid
hydrophilic head (polar group)
hydrophobic tail
contains differentiating group, phosphate, and glycerol
tails of phospholipids
saturated = straight tail, single bonds, full of hydrogen
unsaturated = double bonds, kinked
membrane bilayers
when in an aqueous environment they spontaneously self-associate into a bilayer
polar head interacts with water so face outwards
fluidity of membranes
so a membrane can be deformed without damage being caused
it is carefully regulated as it is important for function, transport, enzyme activity, signalling
factors that affect fluidity
temperature (low=less fluid)
saturation of phospholipids (double bonds=more fluid)
length of tails (shorter=more fluid)
addition of cholesterol (flips how it acts temperature wise)
scramblase
random flip-flop of random phospholipids
flippase
rapid flip-flop pf specific phospholipids in cytosolic leaflet
membrane proteins
have specific funtion
are associated with lipid bilayer
integral membrane proteins
they are directly attatched to the bilayer, either inserted or attatched to a lipid
detergent for extraction
peripheral membrane proteins
can be on either face of the membrane, is bound to other proteins/lipids, bound by non-covalent interactions
gentle extraction methods
transmembrane proteins
they are amphipathic, hydrophilic domains outside cell, hydrophobic membrane spanning domails
can be single/multiple alpha helix or beta barrel
transmembrane protein functions
transporters and channels, anchors, receptors, enzymes
how are transmembranes identified
x-ray crystallography, hydrophobicity plot
monolayer-associated membrane proteins
they are anchored on cytosolic face by amphipathic alpha helix
lipid linked membrane proteins
has GPI anchor (synthesizes in ER lumen and ends up on cell surface) or with another lipid anchor (cytosolic enzymes add the anchor, protein is directed to the cytosolic face)
lateral diffusion of membrane proteins
only exists within the leaflet
FRAP
can be restricted
FRAP
labelled tith fluorescent antibody, photobleached with lazor, observed how long it take for unbleached proteins to move around
