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Illustration of a eukaryotic cell membrane Comparison of a eukaryotic vs. a prokaryotic cell membrane. The cell membrane (also known as the plasma membrane or cytoplasmic membrane, and historically referred to as the plasmalemma) is a biological membrane that separates and protects the interior of a cell from the outside environment (the extracellular space).
The cytoplasm describes all the material within a eukaryotic or prokaryotic cell, enclosed by the cell membrane, including the organelles [1] and excluding the nucleus in eukaryotic cells. The material inside the nucleus of a eukaryotic cell and contained within the nuclear membrane is termed the nucleoplasm .
The cytosol is the site of multiple cell processes. Examples of these processes include signal transduction from the cell membrane to sites within the cell, such as the cell nucleus, [57] or organelles. [58] This compartment is also the site of many of the processes of cytokinesis, after the breakdown of the nuclear membrane in mitosis. [59]
The cell membrane, or plasma membrane, is a selectively permeable [citation needed] biological membrane that surrounds the cytoplasm of a cell. In animals, the plasma membrane is the outer boundary of the cell, while in plants and prokaryotes it is usually covered by a cell wall .
The intracellular fluid (ICF) is all fluids contained inside the cells, which consists of cytosol and fluid in the cell nucleus. [3] The cytosol is the matrix in which cellular organelles are suspended. The cytosol and organelles together compose the cytoplasm. The cell membranes are the outer barrier.
The membrane potential has two basic functions. First, it allows a cell to function as a battery, providing power to operate a variety of "molecular devices" embedded in the membrane. [4] Second, in electrically excitable cells such as neurons and muscle cells, it is used for transmitting signals between different parts of a cell.
These differences cause all cell membranes to be electrically charged, with the positive charge on the outside of the cells and the negative charge on the inside. In a resting neuron (not conducting an impulse) the membrane potential is known as the resting potential , and between the two sides of the membrane is about −70 mV.
Light micrograph of a moss's leaf cells at 400X magnification. The following outline is provided as an overview of and topical guide to cell biology: . Cell biology – A branch of biology that includes study of cells regarding their physiological properties, structure, and function; the organelles they contain; interactions with their environment; and their life cycle, division, and death.