Lecture 5 - Plasma Membrane Flashcards
(23 cards)
what is a plasma membrane
- outer boundary of the cell that separates the cellular contents from the outside world
- 5-10nm structure
explain some of the history of plasma membranes
- found to be composed mostly of lipids, because their dissolving power corresponded to that of oil
- membranes are lipid bilayers
explain the lipid bilayer
- stabilized by van der Waal interactions in the fatty acyl chains
- ionic and hydrogen bonds between the polar head groups with each other and with water
what effect does lipid bilayer fluidity have on the components of the membrane
- components are mobile and capable of coming together for transient interactions
where are carbohydrates located on a biomembrane
- on the exoplasmic leaflet
membranes are lipid-protein assemblies held together by?
- noncovalent bonds
what is the lipid bilayer
- structural backbone and barrier to prevent random movements of materials into and out of the cell
what are membrane proteins
- carryout the more specialized functions
how are proteins present in biomembranes
- individual protein molecules and protein complexes that penetrate a lipid bilayer and extend out into the surrounding aqueous environment
the lipid to protein ratio is linked to function and varies depending on ?
- type of cellular membrane
- type of organism
- type of cell
why do mitochondria have more protein
- proteins need for electron transport
why do myelin sheath have more lipids
- lipids needed for electrical insulation
what are the functions of biomembranes
- compartmentalization
- surrounds cell and organelles and allows different regions of the cell to have specialized activities - scaffold for biochemical activities
- often enzyme and signaling complexes are anchored at membranes - selective permeability barrier
- impermeable to most molecules without the aid of specialized transport proteins
- contains machinery to transport most molecules across the membrane - respond to external signals
- plasma membrane contains receptors that allow cells to respond to signals from their environment - allows them to communicate - crucial to the production of energy
- machinery found in the membranes of chloroplasts and mitochondria
what are phosphoglycerides
- also known as glycerophospolipids
- most abundant class of lipids in most membranes
- all exhibit amphipathic character
how are head groups linked on phosphoglycerides
- linked to glycerol via a phosphodiester bond
describe the different head group of phosphoglycerides
- phosphatidylethanolamine (PE) head group is straight
- phosphatidylserine (PS) -1 charge, head group looks like a cross
- phosphatidylcholine (PC) - head group has 3 methyl groups sticking out
what is important about phosphatidylionsitol
- important role in signal transduction
what are sphingolipids and its properties
- derivatives from ceramide
- a long change amino alcohol
- no glycerol backbone
- additional groups can be added to terminal alcohol
describe the sugars of sphingolipids
- can have single sugars or branched oligosaccharides as head groups
- sugar containing lipids are glycolipids
what are glycolipids
- found on non-cytosolic side of plasma membrane
- sugar groups added in the lumen of the golgi
what are the possible functions of glycolipids
- protect the plasma membrane against harsh conditions
- charged glycolipids may bind and affect the concentration of ions
- may be involved in cell-cell adhesion by bind to lectins (carbohydrate binding proteins)
what is a ganglioside
- multiple sugars added creating hundreds of different combinations
a fatty acid may be..?
- saturated (no double bonds)
- monounsaturated (1 double bond)
- polyunsaturated (many double bonds)
