PHY2011 Lecture Notes - Lecture 3: Kinetic Energy, Phospholipid, Viscosity
20 Jun 2018
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Week 1 L3 (T1L2)–Diffusion through membranes
Membrane characteristics
oFluid – work on a scale of fluidity that depends on:
1. Lipid composition
- Saturated hydrocarbon tails = more viscous
- Unsaturated hydrocarbon tails = more fluid
- Shorter lipids = more fluid
2. Amount of cholesterol
- Increases viscosity, b/c reduces phospholipid movement
3. Temperature
- Higher temp = more fluid
oIncreased fluidity = increased permeability
oDynamic nature of structure –phospholipids can move
Lateral movement (Adjacent phospholipids) –frequent
Flip flop (opposite sides) –rare
Selectively permeable membrane
oFacilitates chemical reactions
oAllows developments of an electrical
potential
oAllows import/export of substances
oPrevents uptake of toxic chemicals (ie
antibiotics)
Filtration –due to hydrostatic pressure
oIe in kidneys
Simple diffusion
oDue to a concentration gradient
oFactors influencing Diffusion
1. Concentration differences/electrochemical gradient (the closer the conc, the
slower the net flow)
2. Temperature (Kinetic energy)
3. Distance (decreases particle concentration)
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