Topic 1.4: Membrane Transport Flashcards
Properties of Membranes (2)
a) Semi-permeable (only certain things can cross)
b) Selective (membranes can regulate material passage)
Types of membrane transport (2)
a) Active (Requires ATP, down concentration gradient)
b) Passive (No ATP, against concentration gradient)
Passive transport
a) Simple diffusion
b) Facilitated diffusion
c) Osmosis
Simple diffusion
a) Net movement of molecules along a concentration gradient
b) Involves small lipophilic molecules (O2, CO2)
Osmosis
Net movement of water molecules across a semi-permeable membrane against a concentration gradient.
Hypertonic solution
a) High solute concentration
b) Gains water
Hypotonic solution
a) Low solute concentration
b) Loses water
Isotonic solution
a) Same solute concentration
b) No net water flow
Negative effects of uncontrolled osmosis on cells
a) Crenation (Hypertonic)
b) Lysis (Hypotonic)
Facilitated diffusion
a) Transport of molecules via a membrane protein
b) Involves large / charged molecules.
Carrier proteins
a) Undergo a conformational change to translocate the solute
b) ATP presence
c) Slow rate of transport
Channel proteins
a) Ions may cross through a pore
b) Along a concentration gradient.
c) Fast rate of transport
Active transport
a) Transport against a concentration gradient
b) Requires ATP
Process of active transport (3)
a) Molecule binds to a transmembrane protein pump
b) Hydrolysis of ATP causes a conformational change.
c) The molecule translocates across the membrane.
Sodium-Potassium Pumps (6)
a) 3 Na+ bind to the sodium-potassium pump.
b) A phosphate group is transferred to the pump via the hydrolysis of ATP
c) The pump undergoes a conformational change, translocating Na+ across the membrane.
d) This exposes two K+ to the extracellular suface of the pump.
e) The phosphate group is released
f) Translocates K+ across the membrane.
