Читать книгу Introduction to the Human Cell - Danton PhD O'Day - Страница 5

The body contains all sorts of “membranes.” Though they share the same name, not all membranes are the same. Membranes of the body are typically collections of cells, proteins and carbohydrates that form various types of connective tissue, mucus membranes, etc. They serve to protect or hold tissues and organs together or to support them, among other functions. Biological membranes or biomembranes all consist of a bilayer of phospholipids within which various types of proteins and varying amounts of cholesterol are present. A single continuous cell membrane completely surrounds each and every cell of the body. It is a specialized biological membrane that not only keeps the cell intact but also regulates what gets in and out of cells.

The cell membrane has other functions as well: it allows cells communicate and to stick together. It has receptors for hormones and other molecules that allow it to receive and interpret messages sent from other parts of the body. Inside the cell, there is a diversity of biomembranes each specialized for certain functions. Biological membranes in the cytoplasm compartmentalize cellular functions: the endoplasmic reticulum, Golgi apparatus, lysosomes, vesicles and vacuoles are each surrounded by a single biological membrane and each of these organelles has specific duties to perform. In contrast, mitochondria and the nucleus are surrounded by two biomembranes. For now, we’ll focus on the cell membrane.

All cells are surrounded by a cell membrane (also called the plasma membrane). This is a biological membrane or biomembrane consisting of a double layer of lipids in which proteins are located. The cell membrane keeps the components of the cell isolated from the external environment. It serves as the communication interface between the cell and its environment. The cell membrane is involved in regulating the flow of materials into and out of the cell, mediating intercellular communication and adhesion and a multitude of other functions.

The structure and functions of the cell membrane have been defined by over a half a century of research using biochemical, physiological, cellular and molecular techniques. In spite of the important and diverse work that has been done in the past to bring us to this understanding, this chapter does not present a complete or historical review. Instead it shows us what we understand about the cell membrane today.