Centrioles: Non Membranous Organelles

Centrioles are non-membranous organelles that are usually located near the Golgi apparatus and the nucleus [30]. Most cells have two centrioles, each made up of nine sets of three microtubules (described later on page #39). Centrioles are hollow and cylindrical and lay next to each other at 90 degree angles [31]. Vital to cellular division, the centrioles function to separate homologous chromosomes in meiosis 1 and sister chromatids during mitosis and meiosis 2. During these processes, the centrioles form fibers, called spindle and aster fibers, which attach to the centromeres and line up the chromosomes or homologous pairs of chromosomes on the metaphase plate. Then, the centriole fibers shorten and pull apart the sister chromatids that make

This organelle can be found both on the rough ER and free in cytoplasm, but the proteins produced in each place have different functions; proteins produced in the cytoplasm are typically used within the cell while proteins produced by the rough ER are usually exported outside the cell. The ribosomes themselves are produced in nucleolus and cells that need a lot of protein have a lot of ribosomes [34]. With larger diameters than microfilaments, microtubules are stiff organelles that help maintain the cell 's shape as part of the cytoskeleton. The cytoskeleton is the structure within the cytoplasm of the cell that helps move organelles inside the cell, therefore microtubules are attributed with the function of intracellular movement [35]. In addition to the cytoskeleton, microtubules also make up the cilia and flagella of the cell. Cilia are small hair-like structures that are found on the free surfaces of some cells. Moving in a back and forth motion, cilia help propel substances along the cell [36]. Similar to the cilia, flagella help propel some gametes (cells with half the number of chromosomes). They are larger than cilia and cells that have flagella usually only have one. Flagella move in a wavelike motion and are often found on the surface of one celled organisms such as sperm [37]. Furthermore, microtubules are made of tubulin proteins. Tubulin can come in the form of alpha tubulin and beta

These other components of the cell membrane serve many functions and move about the phospholipids to form a fluid mosaic image, fluid because of the way the molecules float by each other and mosaic because of the pattern that the different substances create on the surface. There are many proteins in the plasma membrane that contribute to this fluid mosaic including transport proteins. Transport proteins move needed substances through the plasma membrane, some of which might have been otherwise stopped by the phospholipid tails. Other proteins function to provide shape to the cell and to transmit signals into the cell. The carbohydrates attached to the proteins in the plasma membrane also help identify chemical signals while the cholesterol keeps the fatty acid tails from sticking together, which helps the plasma membrane to remain fluid and maintain homeostasis