Matthias Schleiden - Cells

Cells

Discovery and Basic Structure

In 1655, the English scientist Robert Hooke made an observation that would change basic biological theory and research forever. While examining a dried section of cork tree with a crude light microscope, he observed small chambers and named them cells. Within a decade, researchers had determined that cells were not empty but, instead, filled with a watery substance called cytoplasm.

Over the next 175 years, research led to the formation of the cell theory, first proposed by the German botanist Matthias Jacob Schleiden and the German physiologist Theodore Schwann in 1838 and formalized by the German researcher Rudolf Virchow in 1858. In its modern form, this theorem has four basic parts:

The cell is the basic structural and functional unit of life; all organisms are composed of cells.

All cells are produced by the division of preexisting cells (in other words, through reproduction). Each cell contains genetic material that is passed down during this process.

All basic chemical and physiological functions, for example, repair, growth, movement, immunity, communication, and digestion are carried out inside of cells.

The activities of cells depends on the activities of sub-cellular structures within the cell (these sub-cellular structures include organelles, the plasma membrane, and, if present, the nucleus).

The cell theory leads to two very important generalities about cells and life in general:

Cells are alive. The individual cells of your organs are just as alive as you are, even though they cannot live independently. This means cells can take energy (which, depending on the cell type, can be in the form of light, sugar, or other compounds) and building materials (proteins, carbohydrates and fats), and use these to repair themselves and make new generations of cells (reproduction).

The characteristics and needs of an organism are in reality the characteristics and needs of the cells that make up the organism. For example, you need water because your cells need water.

Most of the activities of a cell (repair, reproduction, etc.) are carried out via the production of proteins. Proteins are large molecules that are made by specific organelles within the cell using the instructions contained within the genetic material of the cell.

Cytology is the study of cells, and cytologists are scientists that study cells. Cytologists have discovered that all cells are similar. They are all composed chiefly of molecules containing carbon, hydrogen, oxygen, nitrogen, phosphorus and sulfur. Although many non-living structures also contain these elements, cells are different in their organization and maintenance of a boundary, their ability to regulate their own activity and their controlled metabolism.

All cells contain three basic features:

A plasma membrane consisting of a phospholipid bilayer, which is a fatty membrane that houses the cell. This membrane contains several structures that allow the cell to perform necessary tasks; for example, channels that allow substances to move in and out of the cell, antigens that allow the cell to be recognized by other cells, and proteins that allow cells to attach to each other.

A cytoplasm containing cytosol and organelles. Cytosol is a fluid, consisting mostly of water and dissolved nutrients, wastes, ions, proteins, and other molecules. Organelles are small structures suspended in the cytosol. The organelles carry out the basic functions of the cell, including reproduction, metabolism and protein synthesis.

Genetic material (DNA and RNA), which carry the instructions for