Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
17 Cards in this Set
- Front
- Back
Function of membranes
|
1. Maintaining structural integrity
2. Control passage of molecules 3. Regulating cell-cell interactions 4. Recognition of antigens, foreign cells, neighboring cells via recptors 5. Establishing transport systems for various molecules 6. Transducing extracellular signals into cellular responses |
|
Fluid mosaic model
|
Membrane proteins "floatin" in sea os phospholipids
|
|
Properties of fluid membranes
|
1. Uniform distribution can be acomplished via insertion at localized sites
2. Membranes can reseal 3. Receptor aggregation at localized sites is possible 4. No flip-flopping |
|
Outer leaflet
|
Phosphatidylcholine
Sphingomyelin |
|
Inner leaflet
|
Phosphatidylethanolamine
Phosphatidylserine (-) Phosphatidylinositol |
|
What does cholesterol do?
|
Increases membrane packing
|
|
Glycolipids
|
Derived from sphingosine, polar head group is carbohydrate. ONLY outer leaflet.
Galactocerebroside: main component of myelin sheath Ganglioside: Common, functions poorly understood. |
|
Lipid bi-layer properties
|
Polar head groups, non-polar tails.
Outer and inner different composition. Weakly permeable to water. Very permeable to O2, CO2. Not permeable to macromolecules. Limited permeability to ions. Appears trilaminar under electron microsocpe (interaction of electron0dense stain osmium tetroxide with polar headgroups of membrane lipids but not with central hydrophobic portion of bilayer. |
|
Lipid rafts
|
Microdomains with saturated phospholipids, cholestero, glycolipids, and few proteins (including caveolin). Membrane thicker, proteins restricted from lateral movement.
Functions in T-cell receptor signaling, nutrient absorption in intestine, endocytosis. |
|
Alzheimer's and lipid rafts
|
Abnormal cholesterol metabolism in brain = abnormal lipid raft = generation of amyloid-beta peptide
|
|
Prion diseases (Creutzfeldt-Jacob) and lipid rafts
|
Lipid rafts may provide necessary enviroment to convert normal prion protein to infectious form.
|
|
Integral membrane protein
|
Require disruption of lipid bilayer to release from the membrane.
Transmembrane and covalently attached proteins. |
|
Peripheral membrane protein
|
Can be removed from membrane by gentle extraction (change in pH, salt concentration)
Generally non-covalent interactions with other membrane proteins. |
|
Receptors for chemical messages
|
Transmembrane proteins. Extracellular binds to ligand, intracellular initiates response.
|
|
Receptors for steroid hormones
|
Steroids are lipid soluable and can diffuse through plasma membrane are cytosolic proteins.
|
|
Signal transduction
|
Mechanism by which an extracellular chemical messenger is interpreted into an intracellular response.
|
|
Glycocalyx
|
Carbohydrate rich region on external side of plasma membrane. Formed primarily from carb moieties of membrane glycolipids, glycoproteins, and secreted proteoglycans. Functions to bind food molecules in intestines, recognition of other cells, protection of cells from harsh enviroments (GI tract)
|