The microscopic functional and structural unit of all living organisms. Many, but not all, plant cells contain characteristic features found only in plants, including a rigid outer cell wall, internal vacuoles for storage, and chloroplasts for energy production. In addition to a nucleus, the organelles of eukaryotic cells include the endoplasmic reticulum, Golgi apparatus, lysosomes, mitochondria, peroxisomes, and vesicles. Prokaryotic cells, which are relatively smaller than eukaryotic cells, lack a nucleus or organelles and have a single circular molecule of DNA (chromosome) plus optional, smaller, circular molecules of DNA called plasmids.Įukaryotic cells have a nucleus, membrane-bound organelles, and multiple, compartmentalized molecules of linear DNA. All cells have a plasma membrane, made of lipids and proteins, to regulate substance exchange with the external environment. A cell is the microscopic functional and structural unit of all living organisms.
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