Components of CellsCell Membrane(also known as plasma membrane or plasmalemma) is surrounds all cells. It: 1) separates the inner parts of the cell from the outer environment; and 2) acts as a selectively permeable barrier to allow certain chemicals, namely water, to pass and others to not pass. In multicellular organisms certain chemicals on the membrane surface act in the recognition of self. Antigensare substances located on the outside of cells, virusesand in some cases other chemicals. Antibodiesare chemicals (Y-shaped) produced by an animal in response to a specific antigen. This is the basis of immunity and vaccination.Hereditary material(both DNA and RNA) is needed for a cell to be able to replicate and/or reproduce. Most organisms use DNA. Viruses and viroids sometimes employ RNA as their hereditary material.Retrovirusesinclude HIV (Human Immunodefficiency Virus, the causative agent of AIDS) and Feline Leukemia Virus (the only retrovirus for which a successful vaccine has been developed).
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