The animal plasma membrane is a layer of phospholipids that is entwined with cholesterol and proteins. Cholesterol makes up a small part of the cell membrane's mass and it is present in every cell of the body. Cholesterol maintains the integrity of the cell membrane. It assists in the immobilization of the outer surface of the cell membrane and it reduces the permeability of the membrane to most biological molecules. Cholesterol also perform roles in cell signaling, maintaining fluidity and protecting important proteins in the membrane.
<h3><u>One of the reasons we can't get an accurate count is that the bulk of the things that have yet to be discovered and described are in the realm of the very small: insects, bacteria and other microbes</u></h3>
The answer to finish this sentence would be ''the amount of genetic variation in a population'' because environmental factors can either increase or decrease a population.
