Bio1130 Eukaryote cell architecture

Bio1130 Eukaryote cell architecture - Introduction That all...

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Introduction That all living things are made of cells, a part of the cell theory, may not come as a surprise to you. It may even leave you wondering why such an obvious fact is a theory at all! But, remember what a scientific theory is; it's the closest we get to a fact! Until the microscope was invented and refined, no one was able to complete a survey of living organisms and discover they were all made of cells. Once that happened the cell theory was proposed with cells being the fundamental units of living things and the smallest divisible unit of life. Large organisms are composed of organ systems, consisting of individual organs, formed from tissues that are made up of cells, and all of these levels are living; any smaller than the cell and they aren't. Finally cells only come from the division of previous cells; another version of the Law of biogenesis. In contrast to prokaryotes, eukaryote cells are considerably more complex and usually differentiated from their bacterial counterparts by the presence of a membrane bound nuclear material and an endomembrane system that creates a variety of specialized compartments within the cell with specialized functions. Inside the cytoplasm, the cytoskeleton helps support, and to a certain extent maintains, the shape of the cell. In plants and fungi the cell wall maintains the shape of the cell and is composed of either cellulose or chitin, respectively. The outer limits Plants and fungi have an outer cell wall. In the plants this is composed of cellulose and in fungi the wall is made of chitin; both are carbohydrate polymers. Animals don't have a cell wall. Although there may be a cell wall outside, plant and fungal cells all cells have a outer plasma membrane composed of a phospholipid bilayer. All cells, including cells from both prokaryotes and eukaryotes have this outer lipid layer, the plasma membrane separating the cell’s interior from the surrounding environment. It also regulates the movement of materials into and out of the cell using proteins that are embedded in the membrane. Proteins in the membrane may act as transporters and move materials into and out of the cell. These are transmembrane proteins and another role for this type of membrane protein is to act as a receptor for extracellular signals the cell needs to detect. The phospholipids that make up the membrane have polar heads and non-polar tails and when they form the double layer the tails are oriented in the centre with the heads towards either the aqueous environment surrounding the cell or the cytoplasm inside it.
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This note was uploaded on 01/08/2012 for the course SCIENCE BIO1130 taught by Professor Fenwick during the Fall '11 term at University of Ottawa.

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Bio1130 Eukaryote cell architecture - Introduction That all...

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