organelle

(noun)

A specialized structure found inside cells that carries out a specific life process (e.g. ribosomes, vacuoles).

Related Terms

  • eukaryotic
  • photosynthesis

Examples of organelle in the following topics:

  • Characteristics of Eukaryotic Cells

    • numerous membrane-bound organelles (including the endoplasmic reticulum, Golgi apparatus, chloroplasts, and mitochondria)
    • Typically, the nucleus is the most prominent organelle in a cell.
    • Mitochondria are oval-shaped, double membrane organelles that have their own ribosomes and DNA.
    • All of these organelles are found in each and every eukaryotic cell.
    • Chloroplasts are the organelles that carry out photosynthesis.
  • Mitochondria

    • Mitochondria are organelles that are responsible for making adenosine triphosphate (ATP), the cell's main energy-carrying molecule.
    • Mitochondria are double-membraned organelles that contain their own ribosomes and DNA.
    • Each mitochondrion measures 1 to 10 micrometers (or greater) in length and exists in the cell as an organelle that can be ovoid to worm-shaped to intricately branched.
    • Such functions are often associated with the reduced mitochondrion-derived organelles of anaerobic eukaryotes.
    • This organelle has an outer membrane and an inner membrane.
  • The Endoplasmic Reticulum

    • The endoplasmic reticulum is an organelle that is responsible for the synthesis of lipids and the modification of proteins.
    • These modified proteins will be incorporated into cellular membranes—the membrane of the ER or those of other organelles—or secreted from the cell (such as protein hormones, enzymes).
    • This transmission electron micrograph shows the rough endoplasmic reticulum and other organelles in a pancreatic cell.
  • Levels of Organization of Living Things

    • The biological levels of organization range from a single organelle all the way up to the biosphere in a highly structured hierarchy.
    • Macromolecules can form aggregates within a cell that are surrounded by membranes; these are called organelles.
    • Organelles are small structures that exist within cells.
    • Taken together, all of these levels comprise the biological levels of organization, which range from organelles to the biosphere .
    • From a single organelle to the entire biosphere, living organisms are parts of a highly structured hierarchy.
  • Lysosomes

    • Lysosomes are organelles that digest macromolecules, repair cell membranes, and respond to foreign substances entering the cell.
    • If no food is provided, the lysosome's enzymes digest other organelles within the cell in order to obtain the necessary nutrients.
    • In addition to their role as the digestive component and organelle-recycling facility of animal cells, lysosomes are considered to be parts of the endomembrane system.
    • Other organelles are present in the cell but for simplicity are not shown.
  • Peroxisomes

    • A type of organelle found in both animal cells and plant cells, a peroxisome is a membrane-bound cellular organelle that contains mostly enzymes .
    • Peroxisomes are membrane-bound organelles that contain an abundance of enzymes for detoxifying harmful substances and lipid metabolism.
  • Vesicles and Vacuoles

    • Vesicles can also fuse with other organelles within the cell.
    • Animal cells have a set of organelles not found in plant cells: lysosomes.
    • Enzymes within the lysosomes aid the breakdown of proteins, polysaccharides, lipids, nucleic acids, and worn-out organelles.
    • Many reactions that take place in the cytoplasm could not occur at a low pH, so again, the advantage of compartmentalizing the eukaryotic cell into organelles is apparent.
  • Comparing Plant and Animal Cells

    • Animal cells have another set of organelles not found in plant cells: lysosomes.
    • Enzymes within the lysosomes aid the breakdown of proteins, polysaccharides, lipids, nucleic acids, and even worn-out organelles.
    • Many reactions that take place in the cytoplasm could not occur at a low pH, so the advantage of compartmentalizing the eukaryotic cell into organelles is apparent.
    • Chloroplasts are plant cell organelles that carry out photosynthesis.
    • Some bacteria perform photosynthesis, but their chlorophyll is not relegated to an organelle.
  • Common Bacterial Traits

    • Bacteria do not tend to have membrane-bound organelles in their cytoplasm and thus contain few large intracellular structures.
    • They consequently lack a true nucleus, mitochondria, chloroplasts, and the other organelles present in eukaryotic cells, such as the Golgi apparatus and endoplasmic reticulum.
  • Endosymbiosis and the Evolution of Eukaryotes

    • More detailed electron microscopic comparisons between cyanobacteria and chloroplasts combined with the discovery that plastids (organelles associated with photosynthesis) and mitochondria contain their own DNA led to a resurrection of the idea in the 1960s.
    • The possibility that the peroxisome organelles may have an endosymbiotic origin has also been considered, although they lack DNA.
    • A eukaryote with mitochondria engulfed a cyanobacterium in an event of serial primary endosymbiosis, creating a lineage of cells with both organelles.
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