Here are several practice examples for you to better understand how the electrochemical gradient dictates the direction a given ion will move (i.e. directionality of flux). Example #1: Li+ (cation) Internal concentration of Lithium ions = 8 mM External concentration of Lithium ions = 115 mM Equilibrium potential of Lithium (ELi) = +71 mV 1a. Describe the chemical and electrical driving forces at a membrane potential (Vm) of +71 mV. 1b. Describe the chemical and electrical driving forces at a Vm of +100 mV. 1c. Describe the chemical and electrical driving forces at a Vm of +20 mV. 1d. Describe the chemical and electrical driving forces at a Vm of -25 mV. Example #2: Fr+ (cation) Internal = 99 mM External = 13 mM EFr = -54 mV 2a. Describe the chemical and electrical driving forces at a Vm of -54 mV. 2b. Describe the chemical and electrical driving forces at a Vm of -80 mV. 2c. Describe the chemical and electrical driving forces at a Vm of -10 mV. 2d. Describe the chemical and electrical driving forces at a Vm of +30 mV. Example #3: Be++ (cation) Internal = 55 mM External = 0.1 mM EBe = -84 mV 3a. Describe the chemical and electrical driving forces at a Vm of -84 mV. 3b. Describe the chemical and electrical driving forces at a Vm of -60 mV. 3c. Describe the chemical and electrical driving forces at a Vm of -99 mV. 3d. Describe the chemical and electrical driving forces at a Vm of +8 mV. Example #4: Br- (anion) Internal = 16 mM External = 68 mM EBr = -39 mV 4a. Describe the chemical and electrical driving forces at a Vm of -39 mV. 4b. Describe the chemical and electrical driving forces at a Vm of -55 mV. 4c. Describe the chemical and electrical driving forces at a Vm of -21 mV. 4d. Describe the chemical and electrical driving forces at a Vm of +38 mV.