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cell, in biology, the basic membrane-bound unit that contains the fundamental molecules of life and of which all living things are composed. A single cell is often a complete organism in itself, such as a bacterium or yeast. Other cells acquire specialized functions as they mature.
Cell theory, fundamental scientific theory of biology according to which cells are held to be the basic units of all living tissues. First proposed by German scientists Theodor Schwann and Matthias Jakob Schleiden in 1838, the theory that all plants and animals are made up of cells marked a great
Most cells have three main parts—the cell membrane, the cytoplasm, and the nucleus. The cell membrane is like the skin of the cell. The cytoplasm performs many functions to keep the cell alive.
nucleus, in biology, a specialized structure occurring in most cells (except bacteria and blue-green algae) and separated from the rest of the cell by a double layer, the nuclear membrane.
cell, In biology, the basic unit of which all living things are composed; the smallest structural unit of living matter that is able to function independently. A single cell can be a complete organism in itself, as in bacteria and protozoans .
A cell is a mass of cytoplasm that is bound externally by a cell membrane. Usually microscopic in size, cells are the smallest structural units of living matter and compose all living things. Most cells have one or more nuclei and other organelles that carry out a variety of tasks. Some single cells are complete organisms, such as a bacterium ...
Cell membrane, thin membrane that surrounds every living cell. The cell membrane functions as a barrier, keeping cell constituents in and unwanted substances out, and as a gate, allowing transport into the cell of essential nutrients and movement from the cell of waste products.
membrane, in biology, the thin layer that forms the outer boundary of a living cell or of an internal cell compartment. The outer boundary is the plasma membrane, and the compartments enclosed by internal membranes are called organelles.
The smallest unit of living matter that can exist by itself is the cell. Some organisms, such as bacteria, consist of only a single cell. Others, such as large animals and…
stem cell, an undifferentiated cell that can divide to produce some offspring cells that continue as stem cells and some cells that are destined to differentiate (become specialized). Stem cells are an ongoing source of the differentiated cells that make up the tissues and organs of animals and plants.