Which of the following circumstances allow(s) membranes to bypass transport equilibrium?
1) Transport that is coupled to a thermodynamically favored process, in which the free energy released from the favorable process drives the thermodynamic transport of another reagent
2) Chemical modification of a compound after it crosses to the other side
3) The presence of an electrical potential that is maintained across the membrane
4) All of these circumstances allow membrane transport processes to avoid reaching equilibrium.