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The Cell • The basic living, structural, and functional unit of all organisms Cell Membrane • Floating around in the cell membrane are different kinds of proteins. These are generally globular proteins. They are not held in any fixed pattern but instead float around in the phospholipid layer. Generally these proteins structurally fall into three catagories... Proteins in the cell Membrane • There are carrier proteins that regulate transport and diffusion ! • Marker proteins that identify the cell to other cells ! • And receptor proteins that allow the cell to recieve instructions Phospholipid • This is a simple representation of a phospholipid. the yellow structure represents the hydrophillic or water loving section of the phospholipid. • The blue tails that come off of the sphere represent the hydrophobic or water fearing end of the Phospholipid. Cell Membrane (carrier proteins) • These are carrier proteins. They do not extend through the membrane. They bond and drag molecules through the bilipid layer and release them on the opposite side. Cell Membrane (channel proteins) • In some cases the channel proteins simply act as a passive pore. Molecules will randomly move through the opening in a process called diffusion. This requires no energy, molecules move from an area of high concentration to an area of low concentration. Phospholipid Structure • The two long chains coming off of the bottom of this molecule are made up of carbon and hydrogen. Because both of these elements share their electrons evenly these chains have no charge (gasoline is also a hydrocarbon). Molecules with no charge are not attracted to water; as a result water molecules tend to push them out of the way as they are attracted to each other. This causes molecules with no charge not to dissolve in water (this is why gasoline and water do not mix). At the other end of the phospholipid is a phosphate group and several double bonded oxygens. The atoms at this end of the molecule are not shared equally. This end of the molecule has a charge and is attracted to water. Nucleus • The nucleus is the headquarters of the cell. It regulates all cell activity. It consists of a nuclear envelope, (the outer membrane) and nucleoplasm. In the nucleoplasm you can see chromatin and the nucleolus. Nucleus - Structure - Nucleolus • Within the nucleus are found chromatin and a structure called the nucleolus. Chromatin is DNA in its active form. It consists of DNA looped around histone proteins. The nucleolus is a knot of chromatin. It is the nucleolus that manufactures ribosomes Cytoplasm • The term cytoplasm refers to everything between the cell membrane and the nuclear envelope. It consists of primarily of water. It also contains various organelles as well as salts, dissolved gasses and nutrients. There are 3 groups of organelles in the cytoplasm: Protein producers, Energy Producers and Specialty structures. Ribosomes (protein producer) • The rough E.R. has ribosomes attached to it. This gives it its texture. These ribosome manufacture proteins for the cell. Golgi Complex (Body) (protein producer) • The golgi body is responsible for packaging proteins for the cell. Once the proteins are produced by the rough E.R. they pass into the sack like cisternae that are the main part of the golgi body. These proteins are then squeezed off into the little blebs which drift off into the cytoplasm. The Endoplastic Reticulum • Spreading throughout the cytoplasm is the endoplasmic reticulum. It is a folded system of membranes that loop back and forth giving it a very large surface area. This membrane provides a surface area for cell reactions. It is also the Site of lipid production. Protien Producing Organelles • The E.R. comes in two forms: Smooth E.R. (protein producer) • Smooth E.R. has no ribosomes associated with it Rough E.R. (protein producer) • The rough E.R. has ribosomes Lysosomes (protein producer) • Lysosomes are called suicide sacks. They are produced by the golgi body. They consist of a single membrane surrounding powerful digestive enzymes. Mitochondria (Energy producer) • Power house of the cell. • The mitochondrion is the site of aerobic respiration. Most of the key processes of aerobic repiration occur accross its inner membrane. One theory holds that they evolved from endosymbiotic bacteria. Chloroplast (Energy producer) • The Chloroplast is the photosynthesis. It is here that plant cells trap the energy of light and use it to manufacture food proteins for the cell. Centriole (Specialty Structures) • Centrioles are found only in animal cells. They function in cell division. Notice the 9 sets of 3 arrangement of the protein fibers. Cilia and Flagella (Specialty Structures) • These are hair like extentions off of the cell membrane. Their structures are similar except that cilia tend to be small and numerous and flagella tent to be large and fewer. Their they beat back and forth rythmically. In unicellular organisms their job is locomotion. In large multicellular organisms their role is to move fluid past the cell. Notice the 9+2 arrangement of the microtubles. Vacuoles (Specialty Structures) • Vacuoles are large empty appearing areas found in the cytoplasm. They are usually found in plant cells where they store waste. As a plant cell ages they get larger. In mature cells they occupy most of the cytoplasm. Cell wall (Specialty Structures) • Cell walls are the rigid structure found surrounding plant cells. They provide support for the plant Plastids (Specialty Structures) • Plastids are large organelles found on plants and some protists but not in animals or fungi. They can easily be seem through a light microscope. Chloroplasts represent one group of plastids called chromoplasts (colored plastids). The other class of plastid are called leucoplasts (colorless plastids); they usually store food molecules. Included in this group are amyloplasts or starch plastids shown here in potato root cell.