Organelle
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Organelles are structrues found in the cytoplasm of cells that carry out specific functions. They act as little organs within each cell. The nucleus, mitochondria, and chloroplasts are the only organelles that contain DNA. The Endosymbiotic Theory explains why mitochondria and chloroplasts contain DNA.
Types of Organelles
Organelle | Description | Function in cell |
---|---|---|
Nucleus | Sphere at center of cell surrounded by nuclear membrane | Controlls most cellular functions |
Nucleolus | Solid sphere within nucleus | Begins production of ribosomes |
Rough Endoplasmic Reticulum | Membrane system attached to nucleus | Holds ribosomes, modifies proteins |
Smooth Endoplasmic Reticulum | Same as Rough Endoplasmic Reticulum, but void of ribosomes | Bonds membrane lipids, detoxifies drugs |
Golgi Bodies / Golgi Apparatus | Stack of membranes | Packages proteins and other molecules for export out of cell |
Lysosomes (only in animal cells) | Small spheres | Break down dead organelles and no longer useful molecules |
Vacoules | Membrane covered sacs | Store food and water |
Mitochondria | Membrane covered, and composed of a folded membrane | Change chemical energy from food into forms the cell can use |
Chloroplasts (only in plant cells) | Green, membrane enclosed sacs | Contain the chlorophyll involved in photosysthesis |
Chromoplasts (only in plant cells) | Membrane enclosed sacs | Contain other pigments involved in photosynthesis |
Leukoplasts (only in plant cells) | Membrane enclosed sacs | Convert glucose into starch |
Centrioles (only in animal cells) | Cylindrical, found in pairs | Assist in cellular division |
References
Miller, Kenneth, et. al. Biology. Boston: Prentice Hall, 2006.