Membrane Transport Intro Flashcards
Significance of transmembrane transport
~ able to define its own intracellular medium –> compatible with cell’s replication + metabolism
~ selective transport of nutrients and removal of waste products = v important
List three important roles of transmembrane transport.
Bioenergetics - transport of ions, ATP synthesis etc.
Signal transduction - e.g. action potentials and Ca2+-based signalling
Compartmentalisation - enable metabolism flexibility, storage, lysosomes, vacuoles
What are the three main types of transporter.
PUMPS - low turnover rate, high abundance
CARRIERS - intermediate transport rate
CHANNELS - high turnover rate, passive selective transport, highly regulated
Nernst potential
the transmembrane voltage at which transmembrane ion movement is at equilibrium for a given ion conc. grad.
Influx
passive movement down electrochemical gradient
Efflux
active movement up electrochemical gradient
Electrochemical gradient
~ combination of ion concentration gradient (chemical) and electrical gradients
~ can be quantified and used to determine if ion passage is active/passive
Primary Pumps (4)
uses ATP to pump ions against their electrochem. grad.
~ primary active transport
~ electrogenic
~ establish electrochem. grad. for ‘driver’ ions
Carriers (3)
~ energised by ‘driver’ ion electrochemical gradient
~ secondary active transport
~ can be electrogenic or electroneutral
Types of carriers
~ symporters/co-transporters
~ antiporters/counter-transporters
~ facilitators
Symporters/co-transporters
move substances in the same direction as the ‘driver’ ion
Antiporters/counter-transporters
move substances in the opposite direction as the ‘driver’ ion
Facilitators/uniporters
allow facilitated diffusion passively down electrochemical grad.
Channels (2)
~ always passive down electrochemical grad.
~ defined opera dn shut kinetics
Electroneutral
having no net electric charge
~ moves in 1 +ve ion and 1 negative ion
