Cells

The cell is the basic structural and functional unit of all living organisms.   Some organisms, such as bacteria, are unicellular, i.e., contain one cell.   Humans, are multicellular, having an estimated 100 trillion cells.   There are about 210 distinct kinds of adult human cells, each with a different structure and function.   Every tissue and organ in the human body has specialized cells that enable the tissue and organ to function.  A typical cell diameter is 10 micrometers (10^-6) with a typical cell mass of 1 nanogram (10^-9).   All cells come from preexisting cells.   All vital functions of the body occur within cells.   Cells contain the hereditary information necessary for regulating cell functions and for transmitting information to the next generation of cells.   Each cell is self-contained and self-maintaining; that is, it can take in nutrients, convert these nutrients into energy, carry out specialized functions, and reproduce as necessary.   Each cell stores its own set of instructions for carrying out each of these activities.   Cell metabolism consists of taking in food, building cell components, converting molecules into energy, forming new molecules and releasing wastes.   The functioning of a cell depends upon its ability to extract and use chemical energy stored in the organic molecules contained in food, such as carbohydrates, proteins, fats, and vitamins. ^{Wiki n.p.}

Common Cell Components ^{Wiki n.p.}

There are some differences in cellls, depending on their specific functions, e.g., nerve v. fat cells, but most cells have the parts described below in common.