The Cell Theory

When Schleiden and Schwann proposed the cell theory in 1838, cell biology research was forever changed. The cell theory states that: All life forms are made from one or more cells. Cells only arise from pre-existing cells. The cell is the smallest form of life. The cell theory also provides us with an operational definition of "life." We will learn about prokaryotes, eukaryotes, and viruses.For now time being there are another 4 modern cell theory Modern Cell Theory -has additional 4 statements: the cell contains hereditary information which is passed on from cell to cell during cell division All cells are basically the same in chemical composition and metabolic activities All basic chemical and physiological functions are carried out inside the cells (movement, digestion,homeostasis etc.) Cell activities depends on the activities of subcellular structures within the cell (organelle, nucleus and plasma membrane)

From what I understood cell theory refers to the idea that cells are the basic unit of structure in every living things.. This theory is one of the foundations of biology. The theory says that new cells are formed from other existing cells, and that the cell is a fundamental unit of structure, function and organization in all living organisms.

Two types of cells

There is another basic cell structure that is present in many but not all living cells: the nucleus. The nucleus of a cell is a structure in the cytoplasm that is surrounded by a membrane (the nuclear membrane) and contains, and protects, most of the cell's DNA. Based on whether they have a nucleus, there are two basic types of cells: prokaryotic cells and eukaryotic cells.

Prokaryotic cells are cells without a nucleus. The DNA in prokaryotic cells is in the cytoplasm rather than enclosed within a nuclear membrane. Prokaryotic cells are found in single-celled organisms, such as bacteria. Organisms with prokaryotic cells are called prokaryotes. They were the first type of organisms to evolve and are still the most common organisms today.

Eukaryotes  are organisms whose cells are organized into complex structures by internal membranes and a cytoskeleton. The most characteristic membrane bound structure is the nucleus.. Animals, plants, fungi, and protists are eukaryotes.

Eukaryotic cells allow larger and more complex organisms to be made, and asingle eukaryotes cell complex than prokaryotic cells. Whether eukaryotic cells live singly or as part of a multicellular organism, their activities can be much more complex and diversified than prokaryotic. In prokaryotes, all internal cellular events take place within a single compartment, the cytoplasm. Eukaryotes contain many subcellular compartments called organelles. Even single-celled eukaryotes can display remarkable complexity of function; some have features as specialized and diverse as sensory bristles, mouth parts, muscle-like contractile bundles, or stinging darts.