Biology Unit 2 Db Scie206.Doc
SCIE206-1104A-04 Unit 2 Discussion Board Energy, Metabolism, and Cells Jessica Laymon Plasma Membrane The plasma membrane is a membrane that is extremely thin and fluid, that surrounds, or encloses both eukaryotic and prokaryotic cells. All living cells have plasma membranes; this membrane regulates the interchange of materials between the cell and its environment. The main areas of its structure are a bilayer of phospholipids, and proteins. The phospholipids are responsible for the isolation from its surroundings; it can allow or not allow certain substances in or out.
The proteins are responsible for helping the cell communicate with its environment. Proteins also help move molecules through the bilayer. The plasma membrane is located on the outside of animal cells or beneath the cell wall on plant cells. (Pearson) Bacterial Cell Wall VS. Plant Cell Wall The bacterial cell wall consists mostly of a chemical called peptidoglycan, which is a protein sugar molecule which is an essential need for the bacteria to survive. Plant cell walls contain cellulose, pectin and hemicellulose and have two cell walls, a primary wall that is thin and flexible, and a secondary wall that is thick and contains lignin.
Both the bacterial and plant cell wall are there to surround and protect them from the environment. Cytoskeleton The cytoskeleton is composed of three different types of fibers, microtubules, microfilaments and intermediate filaments. Microtubules are the thickest of the three fibers, making up the cytoskeleton, it is a straight hollow tube made of globular proteins called tubulins. It gives structure and movement of cilia and flagella. Microfilaments are the thinnest of the three filaments; they are solid rods and are active in muscle contraction.
Intermediate filaments provide support for microfilaments and microtubules by holding them in place. (about. com) a cytoskeleton gives mechanical support to the cell and maintains its shape, like bones and muscle. It is very important in animal cells, which don’t have rigid walls, without cytoskeleton it would have no infrastructure. References Biology, Life on Earth with Physiology, Ninth Edition, T. Audesirk, B. E. Byers, Pearson Education, 2011 Chapter 5, pg. 78 About. com, Biology, The Cytoskeleton, http://biology. about. com/od/cellanatomy/a/aa013108a. htm, retrieved from World Wide Web on Oct 12, 2011,