Lipid bilayers assemble spontaneously. Polymerization of organic material happens as water shaken. Scum separates into micelles. But it isn't clear whether this happened BEFORE there was genetic material to be surrounded and protected. Oparin and Fox argue that the membranes came first. DeDuve argues that the membrane came LATER, to protect genetic messages.* The first membrane, he argues, was made of loose proteins into which fats were inserted later.

Changes in obtaining food came first --the pumps and transporters in the membranes that allowed food to come in and waste to go out. Salt, for example, was important to control, as the first cells evolved in a salty ocean.

Receptors on the surface of the cell membrane probably came later, as well as flagella to aid movement.

 The cell membrane acts as STRUCTURAL SUPPORT and INSULATION, but also as a FILTER, letting some things in and pushing other stuff out.

 Different groups of components come together in the lipid bilyer membrane:

1. Pumps and transporters to move/regulate very specific particles, like ions. See About pores.

2. Factories (e.g. enzymes, sugar-adding systems, and secretion regulators) for making wall components

3. Surface receptors (e.g. chemical responders that bind to a molecule and this triggers a shape change further away at an "effector site", like a molecular motor changing so that it moves a flagella.

Cystic Fibrosis (See Zoom) is a disease of the secretions such as mucus, which thicken because water is kept within the cell. A protein is missing that forms a pore on the membrane for Chloride ions.

 Cholera is a disease in which the secretory cells of the small intestine are made to expel their water quickly. The victim dies of shock and kidney failure. The solution is Rehydration Therapy.

There is a possibility that the body developed different responses to Cholera over time, including the Cystic Fibrosis response.

More about diseases: Bacteria that cause diseases can be attacked by attacking their cell membranes. Penicillin prevents bacteria from building their cell wall.