An organelle is any part of a cell having a specialized function. Organelles are located within the cytoplasm, or the area between the cell wall and the nucleus. Organelles maintain the integral activities within the cell. Without these vital structures, the cell loses its ability to function and eventually dies.
Active cells use vacuoles, vesicles and endoplasmic reticulum as storage organelles. Vacuoles are outgrowths of the cell membrane; they are both composed of the same material. Vacuoles store enzymes, water and food for the cell.
Vesicles are formed from the Golgi apparatus, another cell organelle. Vesicles store and carry proteins to the cell membrane and to other organelles. The endoplasmic reticulum is a transitory storage area for manufactured protein in the cell.
Ribosomes and lysosomes are involved in cell synthesis. Ribosomes, consisting of ribonucleic acid (RNA), are distributed evenly in the cytoplasm and are especially abundant in the active growth phase.
Lysosomes break down various materials in the cell: fats, proteins, waste materials, carbohydrates and other large molecular structures. Once broken down, they are stored within the cytoplasm for future cell-building activities. Lysosomes utilize hydrolytic enzymes to accomplish synthesis.
Centrioles support the cell while it undergoes cell division. During this activity, centrioles replicate to produce centrosomes with a pair of centrioles in each. The centrosomes migrate to opposite ends of the cell and microtubules spindle out of each of the centrioles, eventually separating each centrosome into daughter cells.
Supporting organelles also include mitochondria and chloroplast. The mitochondria, found in all eukaryotic cells, produce energy and are cellular respiration sites. Chloroplasts, found only in plant cells, produce food for the plant.
Small microscopic organisms also have organelles used for moving. The cilia in paramecium are short, hairlike protrusions that serve in cell motility through undulating action and also in movement of materials across the cell membrane. The relatively longer flagella are whiplike projections that function in cellular push and pull movement.