Transport across membranes AS Flashcards
structures in a cell membrane
phospholipid bilayer, intrinsic proteins, extrinsic proteins, cholesterol (stability) and glycoproteins (recognition site)
structures in a phospholipid
2 fatty acids, glycerol, phosphate. hydrophobic tail and hydrophilic head so from bilayer
what sort of molecules can and can’t diffuse through a cell membrane
lipid soluble molecules, water and other small substances can. water soluble ones and large ones can’t
define the use of fluid and mosaic in the fluid mosaic model
fluid, molecules are moving. mosaic, made up of proteins and phospholipids
define diffusion
passive process of net movement of particles from area of high to low concentration. down concentration gradient
ways of increasing rate of diffusion
bigger surface area, short diffusion pathway, higher temperature, bigger concentration gradient
why does higher temperature increase rate of diffusion
more kinetic energy so move faster
define facilitated diffusion
molecules too large to diffuse across membrane can go via specific protein channels/carriers
define osmosis
net movement of water from an area of high concentration to an area of low concentration across a partially permeable membrane. passive.
when would carrier proteins be a limiting factor
when they are fully saturated with molecules
do animal cells in a hypertonic solution burst or shrink
shrink
do animal cells in a hypotonic solution burst or shrink
burst
define active transport
net movement of molecules from an area of low concentration to high concentration using energy and carrier proteins. requires ATP
how a substance moves across membrane via carrier proteins using active transport
ion binds to carrier protein ATP binds to inside of proteins causes protein to change shape ion released Pi released from protein
steps in co-transport
sodium ions actively transported from ileum epithelial cell to blood
maintains diffusion gradient for sodium to enter from gut
and glucose with it
glucose enters by facilitated diffusion
