Simple - not using a protein, molecule can pass between phospholipids or through another medium such as air or water

Cell mediated - using a protein to cross the cell membrane

Passive - driven by concentration gradient, no energy input by cell required for movement, gradient not required

Brownian motion - random movement of particles in liquid or gas, no change in concentration over time

Simple diffusion - movement of molecules from area of high concentration to area of low concentration leading to change in concentration over time

• Concentration gradient - difference in concentration between two areas

  • molarity (M or mM) - concentration of solute in solution, moles/L or millimoles/L

• Temperature - average kinetic energy of the sample

• Molecular size (dalton, amu) - size of the molecule

• Membrane permeability

  • Thickness

  • Resistance

  • Surface area

Electrochemical gradient - gradient consisting of both charge and concentration

Eq potential - charge gradient equal and opposite to concentration gradient in force

Osmosis - net movement of water across a semi-permeable membrane

Osmolarity (OsM, mOsM) - concentration of active particles in solution in osmoles or millisosmoles

• Size and type of particle do not matter as long as it is water soluble

• (molarity)(number of particles from each molecule) = osmolarity

Osmotic gradient - difference in osmolarity across a semipermeable membrane

Osmotic pressure - pressure generated when water pushes toward the side with higher osmolarity in a system with a fixed volume (or the pressure required to prevent osmosis)

Tonicity - describes the effect of a solution on the volume or tension of a cell

• Isotonic - no net osmosis, no effect on cell volume or tension

• Hypertonic - net osmosis out of cell, decreases cell volume and tension → crenation of cell

• Hypotonic - net osmosis into cell, increases cell volume and tension → swell and lyse of cell

Transport proteins (transporters, channels, ATP powered pumps)

• Subtypes

  • Uniporter - moves one type of molecule

  • Cotransporter - moves more than one type of molecule

    • Symporter - same direction

    • Antiporter - oppsite directions to each other

  • Unidirectional - only operates in one direction

  • Bidirectional - operates in either direction depending on conditons

• Conformational change - change in the 3D shape of a protein

• Specificity - specific based on size, shape, charge of substrate

• Competition - molecules seem to compete for space, but one with greater concentration gradient will be transported at greater rate

• Saturation - substrate concentration at which all binding sites are constantly occupied

  • Vmax/Tmax - highest rate of transport possible without adding more proteins, at or above saturation concentration

Facilitated diffusion - passive movement of molecules across a cell membrane from high concentration to low concentration via a transmembrane protein, leading to a change in concentration over time

• Binding of a substrate causes conformational change

Primary active transport - movement of molecules across a cell membrane via a transmembrane protein using ATP as the energy source

• Substrates must still bind, but do not drive conformational change

• Phosphorylation/dephosphorylation causes conformational changes

• ATP → ADP + Pi

• Example: Na+/K+ pump - pumps 3 Na+ out, 2 K+ in, breaks down 1 ATP

Secondary active transport - movement of one molecule from low concentration to high concentration coupled with the movement of another molecule from high concentration to low concentration using the concentration gradient of the second molecule as the energy source

• Example: Ca2+/Na+ antiporter - allows 1 Na+ in, pumps 1 Ca2+ out