University:
University of Wolverhampton
Course:
4PY019 | Pharmacy
Academic year:

2024
Views:

185

Pages:

3
Author:

Sara

plasma membrane selectively permeable controls enter and exit fluid mosaic model phospholipid bilayer heads out tails in water soluble retained selective permeability of cell membrane highly impermeable to most polar and charged molecules passive diffusion passage through lipid portion of cell membrane no energy no proteins passive transport no energy conc or electrical gradients active transport energy needed works against conc/elec gradient requirement for molecule for transport must be in solution dissolved simple diffusion - entropy increase in entropy so decrease in free energy random movement of molecules Brownian motion what molecules cross by simple diffusion? small lipid soluble molecules lipid soluble vitamids drugs process of passive diffusion break bonds with aqueous medium enter lipid region and cross via diffusion leave membrane at other side reform bonds with medium transmembrane passage is high energy energy changes in membrane transport state and an activation barrier must be overcome diffusion coefficient conc gradient rate of diffusion depends on : 1/3 thickness of membrane surface area diffusion using proteins allows polar and uncharged molecules to pass facilitated diffusion carrier - binds on one side, conformational changes occur, molecule passes through carrier and channel proteins channel - open pores through membrane ion channels specific to ion primary active transport relies on ATP secondary active transport electrochemical gradient Symport pumps (symporters) move two or more substances in the same direction antiports two substances in opposite directions ABC transporters carrier proteins that use energy from ATP to transport solutes Endocytosis form vesicle moving materials inside cell e.g drug delivery to cells by nanoparticles what are the different types of microscopic techniques that have been used to visualise cell membranes and develop the current Fluid Mosaic model? TEM - resolution 0.2nm - magnification = x 5,000,000 - requires staining Freeze Fracture Electron Microscopy specimen is frozen and fractured replica is created transmembranes proteins fluorescence microscopy specific proteins are tagged fluorescently and visualised identfy specific proteins in the membrane FRAP fluoroscence labelled phospholipds spot is photobleached 2/3 turns white describe a technique that has been used spot turns green as fluid movement to investigate cell membrane fluidity? proteins even out colour moving by diffusion Edidin Experiment proteins move laterally within membrane what causes cell membrane fluidity to decrease, and what are the consequences of this? temperature - causes leaks, proteins - more protein, more packed cholestrol - less cholestrol - more fluidity fatty acid chains -> saturated - no double bonds- more rigid unsaturated - kink --> less rigid alpha helix --> recognition proteins, receptors what are the two known structural classes of membrane proteins and what are a helical bundle --> enzymes, transtheir functions? porters, receptors b barrel --> transporters what is the main difference between a membrane raft and a cell membrane? cholestrol glycosylated proteins phospholipids are saturated and packed together float freely more rigid compared to bilayer 3/3