Structure of a Generalized Eukaryotic Cell

We have already seen that the cell is the structural and functional unit of living things. There are different types of cells, having different shapes, structures and functions. A typical cell or a generalized cell has been theoretically created so that structures and functions of cell’s components may be easily studied and understood. Almost all cells have the following four characteristics.

1. A surrounding membrane or the plasma membrane.

2. A thick fluid enclosed by this membrane that along with the other cell contents is called protoplasm.

3. Organelles are located within the protoplasm that carry out certain cellular functions.

4. A control center called nucleus that contains the hereditary material DNA.

A generalized structure of a eukaryotic cell is discussed as seen under light and electron microscope. The fine structure of the cell as seen with electron microscope is known as ultra-structure.

Electron microscopic structure of a plant cell

Plasma Membrane

Every cell is bounded by plasma membrane Protoplasm is a semi fluid with cell contents, including the cell organelle and the nucleus of the cell. The membrane is also called cell membrane, is ultra-thin, delicate and elastic. It gives shape and mechanical support to the cell. Chemically cell membrane consists of proteins 60-80%, lipids 20-40% and small quantity of carbohydrates.

Fluid Mosaic Model

In 1972 S. Singer and G. Nicolson introduced the fluid mosaic model of membrane structure. This model proposes that the membrane is a phospholipids’ bi-layer in which protein molecules are either partially or wholly embedded. The proteins are scattered throughout the membrane in an irregular pattern that can vary from membrane to membrane. 

Electron microscopic structure of an animal cell