Biology. a usually microscopic structurecontaining nuclear and cytoplasmic materialenclosed by a semipermeable membrane and, inplants, a cell wall; the basic structural unit of allorganisms.
the semipermeable membrane enclosing thecytoplasm of a cell.
the definite boundary or wall that is part of theouter structure of certain cells, as a plant cell.
Cell Biology. a specialized part of a cell havingsome specific function; a cell organ.
Biology. an aggregate of similar cells and cellproducts forming a definite kind of structuralmaterial with a specific function, in a multicellularorganism.
Biology. a grouping of tissues into a distinctstructure, as a heart or kidney in animals or aleaf or stamen in plants, that performs aspecialized task.
having or consisting of a single cell.
composed of several or many cells.
any organism capable of self-nourishment byusing inorganic materials as a source of nutrientsand using photosynthesis or chemosynthesis as asource of energy, as most plants and certainbacteria and protists.
Biology. an organism requiring organiccompounds for its principal source of food.
any cellular organism that has no nuclearmembrane, no organelles in the cytoplasm exceptribosomes, and has its genetic material in theform of single continuous strands forming coils orloops, characteristic of all organisms in thekingdom Monera, as the bacteria and blue-greenalgae.
any organism having as its fundamentalstructural unit a cell type that contains specializedorganelles in the cytoplasm, a membrane-boundnucleus enclosing genetic material organized intochromosomes, and an elaborate system ofdivision by mitosis or meiosis, characteristic of alllife forms except bacteria, blue-green algae, andother primitive microorganisms.