The organelles or cellular organelles are the structures that are inside every cell. They vary in morphology and differ from each other by the function that each one fulfills within the cell. For instance: the mitochondria, the Golgi apparatus, the ribosomes.
Organelles are present in eukaryotic and prokaryotic cells. The type and number of organelles that a cell has depends directly on its function and structure. For instance: plant cells have the chloroplast organelle (which is responsible for photosynthesis).
Organelles in eukaryotic cells
Eukaryotic cells are those that have a cell nucleus that contains DNA. They are present in unicellular and multicellular organisms. For instance: animal cell, plant cell.
This type of cell is made up of a structure that has a membrane, a cell nucleus and a cytoplasm (where the largest number of cell organelles are found). Organelles allow eukaryotic cells to be more specialized than prokaryotic cells.
Organelles in prokaryotic cells
Prokaryotic cells are those that do not have a cell nucleus. They are present in unicellular organisms. They have a smaller structure and are less complex than eukaryotic cells. For instance: the bacteria, the arches.
Unlike eukaryotic cells, prokaryotes have less variety of organelles in their structure, which vary according to the characteristics and functions of each cell and are present only in some. For instance: ribosomes or plasmids.
Prokaryotic cells share the membrane, cytoplasm, ribosomes, and genetic material with the eukaryotic cell.
Examples of organelles in eukaryotic cells
- Cellular wall. Rigid structure that provides protection to cells found in plants, fungi, and some prokaryotic cells. It is made up of carbohydrates and proteins. This cell wall protects the cell from the external environment.
- Plasma membrane. A thin lipid bilayer that contains protein molecules. It is elastic and its function is to regulate the entry and exit of substances into the cell. Protects the structure and integrity of the cell from external environmental factors. It is also present in prokaryotic cells.
- Rough endoplasmic reticulum. A network of membranes that is present in almost all eukaryotic cells. Its function is the synthesis and transport of proteins. It has ribosomes that give it its rough appearance.
- Smooth endoplasmic reticulum. Membrane that continues the rough endoplasmic reticulum but does not possess ribosomes. Its functions include cell transport, lipid synthesis and calcium storage.
- Ribosomes. Supramolecular complexes that are abundantly present in almost all eukaryotic cells. Its function is to synthesize proteins from the information contained in DNA. They are found free in the cytoplasm or attached to the rough endoplasmic reticulum. They are also present in prokaryotic cells.
- Golgi apparatus. Series of membranes whose function is to transport and pack proteins. It is responsible for forming gluco-lipids and gluco-proteins.
- Mitochondria. Structures of elongated or oval shape responsible for providing energy to the cell. They synthesize Adenosine Triphosphate (ATP) through cellular respiration. They are found in almost all eukaryotic cells.
- Vacuoles. Structures that are present in all plant cells. They vary depending on the cell to which they belong. Their function is storage and transportation. They contribute to the growth of plant organs and tissues. In addition, they intervene in the process of homeostasis (regulation of the body).
- Microtubules. Tubular structures that have among their functions: intracellular transport, movement and organization of organelles in the cell and intervention in cell division (both in mitosis and meiosis).
- Vesicles Intracellular sacs whose function is to store, transmit or direct cellular waste. They are separated from the cytoplasm by a membrane.
- Lysosomes Spherical bags that have digestive enzymes. Their functions include protein transport, cellular digestion and phagocytosis of pathogens that attack the cell. They are present in all animal cells. They are formed by the Golgi apparatus.
- Nucleus. Membranous structure that contains DNA within macromolecules called chromosomes. It is present only in eukaryotic cells.
- Nucleolus Region within the nucleus composed of RNA and proteins. Its function is the synthesis of ribosomal RNA.
- Chloroplasts. Plasts found exclusively in algae and plant cells. They are responsible for carrying out the photosynthesis process in the cell. They have internal sacs that contain chlorophyll.
- Melanosomas. Spherical or elongated structures that contain melanin, the pigment that absorbs light. They are found in animal cells.
- Centrosome. Microtubule organizing center present in some animal cells. Participates in cell division and transport processes. Organize the microtubules of the cell.
- Cytoskeleton A framework of proteins that gives structure and organizes the internal components of the cell. It participates in intracellular traffic and cell division.
- Cilia. Small, short and numerous villi that allow cell movement and transport. They are found on the surface of many types of cells.
- Flagella. System of long and sparse membranes that allow the movement of cells and contribute to the capture of food.
- Peroxisomes. Vesicle-shaped structures that fulfill metabolic functions. They are found in most eukaryotic cells.
- Amyloplasts. Plasts found in some plant cells whose function is the storage of starch.
- Chromoplasts. Plasts found in some plant cells that store the pigments that give plant flowers, stems, fruits, and roots their color.
- Proteinoplasts. Plasts found in some plant cells whose function is to store proteins.
- Oleoplasts. Plates found in some plant cells whose function is to store oils or fats.
- Glioxisome. A type of peroxisome present in some plant cells that converts lipids into carbohydrates during seed germination.
- Acrosome. Vesicle located at the end of the sperm head that contains hydrolytic enzymes.
- Hydrogenosome. Membrane-bounded structure that produces molecular hydrogen and ATP.
Examples of organelles in prokaryotic cells
- Nucleoid. An irregularly shaped cell region of prokaryotic cells that contains the cell’s DNA.
- Plasmids Circular structures that contain the genetic material of the cell. They are also called “mobile genes.” They are present in bacteria and archaea.
- Pili. Extensions found on the surface of many bacteria. They fulfill different functions such as the movement of the cell or the connection between bacteria.