Bacteria are prokaryotic and unicellular organisms. Bacteria have a simple organization; they contain an external cell wall, a plasma membrane, circular DNA within the cytoplasm and ribosomes for protein synthesis. Some bacteria are encapsulated, meaning that they have a polysaccharide capsule outside their cell wall.
A plasma membrane and a cell wall are not the same thing. The plasma membrane, also called the cell membrane, is the outer membrane common to all living cells, made of a phospholipid bilayer, embedded proteins and some bound carbohydrates.
Because cell membranes are fragile, in some types of cells, there are also external structures to support and protect the membrane, like the cellulose wall of plant cells and the chitin wall of some fungi cells. Most bacteria also have an outer cell wall made of peptidoglycans and other organic substances.
The main components of the plasma membrane are phospholipids, proteins and carbohydrates. Phospholipids are amphipathic molecules that are regularly organized in the membrane according to their polarity: two layers of phospholipids form the lipid bilayer, with the polar part of the phospholipids pointing to the exterior part of the layer and the non-polar phospholipid chains toward the interior. Proteins can be found embedded in the lipid bilayer. In addition, there are also some carbohydrates bound to proteins and to phospholipids in the outer surface of the membrane.
The plasma membrane is the outer membrane of a cell, it encloses the cell itself, maintaining specific conditions for cellular function within the cell. Since it is selectively permeable, the plasma membrane plays an important role in the entrance and exit of substances.
There are no pluricellular bacteria. All bacteria are unicellular and prokaryotic.
In bacteria, genetic material is contained in the cytosol and there is no internal membrane that encloses a nucleus.
Cells can be classified as eukaryotic or prokaryotic.
Prokaryotic cells are those that do not have an enclosed nucleus. Eukaryotic cells are those with a nucleus enclosed by a membrane.
Viruses are considered the only living organisms that do not have cells. Viruses are made up of genetic material (DNA or RNA) enclosed in a protein capsule. They do not have membranes, cell organelles, or own metabolism.
Cell theory states that the cell is the basic unit of living organisms.
Before the discovery of the cell, people were unaware that living organisms were made of building blocks like cells.
Cell theory is one of the basic theories of biology.
