Semi-permeable phospholipid membranes provide selective permeability of molecules inside the cell, and also inside membraneless organelles in modern cells. However, phase-separated systems like coacervates and membraneless organelles also have selective partitioning activity without a membrane due to a clear chemical boundary between the condensed interior and the dilute exterior. The partitioning property leads to the maintenance of an out-of-equilibrium state inside the coacervate, resulting in the emergence of chemical gradients (facilitating the movement of molecules from their interior to exterior and driving electrochemical processes) in coacervates and also enabling control of different encapsulated biochemical reactions, similar to both modern cells and membrane-bound protocells. Inside coacervates, selective partitioning of molecules has also been shown both to accelerate the rate of reactions by concentrating solutes and reactants and to inhibit reactions by selectively compartmentalizing enzymatic/reaction substrates and separating them from each other; similar chemical processes also take place in membraneless organelles. Coacervates can also assemble and disassemble readily and completely in the presence or absence of stimuli like pH, temperature, etc. Assembly of coacervates themselves can promote/inhibit certain reactions, and the disassembly of these coacervates will lead to a complete reversal of the reaction kinetics.