In the cytoplasm, materials are organized, separated, and sorted by membranes. Cells exploit the selective permeability of these membranes to partition populations of molecules and generate chemical energy for the cell

Question

Use the principles of the first and second laws of thermodynamics to explain how membranes can be used to produce chemical energy.

Answer 1

When one type of molecule accumulates at a higher concentration on one side of the membrane, the molecules become "organized" by having their movement limited to the space they occupy. The second law of thermodynamics indicates that, if allowed to do so, the molecules would move across the membrane until there is an equal distribution of molecules on either side. The accumulation of molecules on one side of the membrane represents a store of potential energy. The first law of thermodynamics tells us that this energy will not be lost, but rather converted into a different type of energy. First, when the molecules are then allowed to move across the membrane, this potential energy is converted into kinetic energy. The kinetic energy of molecules moving through a protein channel to cross the membrane is often linked to conformational changes in the protein, promoting specific chemical reactions.