Cytoplasmic organelles are small cytoplasmic structures that carry out specific functions. Cytoplasmic organelles are classified as membranous or non-membranous organelles, based on whether a membrane surrounds them. The membranous organelles of cytoplasm are endoplasmic reticulum, Gogli complex, mitochondria, plastids (in animal cells) and lysosomes (in plant cells) while non-membranous organelles of cytoplasm include ribosomes, cytoskeleton and centrioles. Let us study the structure and function of each of these cytoplasmic organelles in details.
The endoplasmic reticulum (ER) is an extensive system of folded membranes dividing into compartments and channels the interior of eukaryotic cells. The ER is the largest of the inner membranes. The term endoplasmic means "in the cytoplasm," and for "a small net" the term reticulum is Latin.It weaves via the inside of the cell in sheets, making a series of channels between its folds. The two largest of the many compartments in eukaryotic cells are the inner region of the ER, which is called the cisternal space, and the outer region, the cytosol.
Ultimately, most of the proteins produced by ribosomes attached to rough ER are transported to other cell regions. The transportation path step is through an organelle called the Golgi complex. It consists of 3 to 20 cisterns that look like a pita bread stack. The cisterns are often curved; giving the Golgi complex a cuplike shape Proteins synthesized by ribosomes on the rough ER are surrounded by a portion of the ER membrane that eventually buds from the surface of the membrane to form a vesicle of transport. The transport vesicle fuses into the cistern with a cistern of the Golgi complex. The proteins are altered and move through vesicles that bud from the edges of the cisternae from one cistern to another. Cisternal enzymes change the proteins into glycoproteins, glycolipids and lipoproteins. A few of the processed proteins leave the cisternae in secretory vesicles that produce the proteins to the plasma membrane detached from the cistern, where they are released by exocytosis. Other processed proteins leave cisterns in vesicles which actually deliver their contents to the membrane of the plasma. Finally, in vesicles called storage vesicles, some processed proteins leave the cisternae.
Lysosomes are formed from complexes in Golgi and actually look like spheres confined to the membrane. Lysosomes have only one membrane and lack internal structure, unlike mitochondria. But they contain as many as 40 powerful digestive enzymes that can break down different molecules. In addition, these enzymes can also digest cell - entry bacteria. Human white blood cells contain large numbers of lysosomes, which use phagocytosis to ingest bacteria.
In the cytoplasm of most eukaryotic cells, spherical or rod-shaped organelles called mitochondria. The number of mitochondria per cell varies widely between different cell types. A mitochondrion is a double membrane similar to the plasma membrane structure. The outer mitochondrial membrane is smooth, but in a series of folds called cristae, the inner mitochondrial membrane is arranged. The mitochondrion's center is a semifluid substance called the matrix. The inner membrane provides an enormous surface area on which chemical reactions can occur due to the nature and arrangement of the cristae. Some proteins that function in cellular respiration are located on the cristae of the inner mitochondrial membrane, including the enzyme that makes ATP, and many of the metabolic steps involved in cellular respiration are concentrated in the matrix. Because of their central role in ATP production, mitochondria are often called the "cell powerhouses".
Ribosomes that are also found free in the cytoplasm are attached to the outer surface of the rough endoplasmic reticulum. Ribosomes are the cell sites of protein synthesis. Eukaryotic endoplasmic reticulum and cytoplasm ribosomes are somewhat larger and denser than prokaryotic cells. These eukaryotic ribosomes are 80S ribosomes, each consisting of a large 60S subunit consisting of three rRNA molecules and a smaller 40S subunit consisting of one rRNA molecule. The subunits are produced separately in the nucleus and exit the nucleus once produced and join in the cytosol together.
The cytoplasmic matrix contains the many organs of eucaryotic cells. One of the cell's most important and complex parts is the matrix. It is the organelles ' "environment" and the location of many important processes of biochemistry.