QUESTION: What is the importance of the cell membranes to life on the planet? ANSWER: All life forms on Earth exist either as single cells or as collections of cells that have a plasma membrane at their periphery (though some cells have cell walls outside their plasma membrane). The lipid-bilayered plasma membrane exists in all living things, as an inevitable structure for the maintenance of cellular homeostasis. It also contributes to the structural integrity of the cell.
It is permeable to lipid-soluble substances such as carbon dioxide and oxygen, and also a major barrier to hydrophilic substances such as glucose and ions. These joint morphologic and physiologic roles sustain metabolic activities that the cell; it is important for the maintenance of ionic and osmotic concentration of organic and inorganic molecules across it. The importance of the plasma is explicitly illustrated when the membrane loses its permeability: in this situation, there is loss of homeostasis and the cell may progress to death.
Indeed, membrane damage is central to cell death and this is the reason even primordial organisms require plasma cell membrane for survival. The importance of cell membrane is the reason there are no living things without a membrane at their periphery. Apart from the plasma membrane, organelles within the cell also need membrane to protect their contents from leaking into the cytoplasm; one of such is the lysosome whose hydrolytic enzymes are destructive to the cell. Others are endoplasmic reticulum, mitochondria, peroxisomes and Golgi bodies.