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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
Cell biology is the study of cells—the fundamental units of structure and function in living organisms. Cells were first observed in the 17th century, when the compound microscope was invented.
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 .
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.
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.
A plant cell is the basic unit of all plants. Plant cells, like animal cells, are eukaryotic, meaning they have a membrane-bound nucleus and organelles. Their characteristic cell wall is composed of cellulose, and they contain chloroplasts for photosynthesis.
Red blood cell, cellular component of blood that carries oxygen from the lungs to the tissues and gives vertebrates’ blood its characteristic color. The mature human red blood cell is small, round, and biconcave. Red blood cells also carry carbon dioxide, a waste product, to the lungs, where it is excreted.
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.
Reproduction, process by which organisms replicate themselves. Reproduction is one of the most important concepts in biology: it means making a copy, a likeness, and thereby providing for the continued existence of species. Learn more about the process of reproduction in this article.