noun, plural: organelles. A membrane-bound compartment or structure in a cell that performs a special function. Supplement. A eukaryotic cell contains many organelles, for example, the nucleus, endoplasmic reticulum, golgi apparatus, mitochondria, and chloroplast (plastid).However, not all these organelles are found in only one cell or in an organism. The chloroplast, for instance, is abundant in plant cells but not in animal cells.upplement. A eukaryotic cell contains many organelles, for example, the nucleus, endoplasmic reticulum, golgi apparatus, mitochondria, and chloroplast (plastid). However, not all these organelles are found in only one cell or in an organism.
Definition. An ANA test detects antinuclear antibodies (ANA) in your blood. Your immune system normally makes antibodies to help you fight infection.n ANA test detects antinuclear antibodies (ANA) in your blood. Your immune system normally makes antibodies to help you fight infection.
In contrast, antinuclear antibodies often attack your body's own tissues â specifically targeting each cell's nucleus. In most cases, a positive ANA test indicates that your immune system has launched a misdirected attack on your own tissue â in other words, an autoimmune reaction.