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Transcript
Chapter 4 Schwann, Schleiden and Virchow are credited with coming up with the basics of the cell theory 3 components: ◦ 1.All living organisms are made up of cells ◦ 2.Cells are the basic units of structure and function in living organisms. ◦ 3.All cells come from cells that existed before them by cellular reproduction. http://www.youtube.com/watch?v=AeygTtDx2W8 Every cell has the following main characteristics: ◦ ◦ ◦ ◦ Cell membrane Cytoplasm DNA Ribosomes Antone von Leeuwenhoek assembled the first microscope that was useful for scientific research. Compound light microscopes reflect light through a set of lenses and the specimen to magnify the specimen. See handout for the parts of the microscope – you must know it. http://www.youtube.com/watch?v=3emmlXcV-MU&feature=related Two important characteristics that determine the quality of a light microscope: ◦ Magnification – an increase in the apparent size of an object. We calculate magnification by the following: Magnification of eyepiece x magnification of objective lens = total magnifying power • Resolution – the measure of clarity of an image. As the magnification increases, the resolution of the image decreases. Some microscopes use beams of electrons for magnification instead of light – electron microscopes Scanning electron microscope (SEM) – used to study the detailed architecture of the surface of the object. Forms a 3D image, but does not show the inside of the object. Transmission electron microscope (TEM) – used to provide a detailed 2D image of the inside structure of the object that is viewed. http://www.cellsalive.com/howbig.htm Cells are microscopic, they are visible only with light microscopes. Most of their size ranges from 1-100 µm. Cells are small, because they have to be able to carry materials from one side of the cell to the next in a short period of time. Cells must have a large enough surface area to be able to take in nutrients and oxygen and release waste quickly. Prokaryotic cells – ◦ small cells (about 1-10 µm) that do not have a nucleus and membrane-bound organelles ◦ Found in bacteria and archaebacteria Prokaryotic Cell Organelles: ◦ Nucleoid region – part of the prokaryotic cell where the DNA is found ◦ Cell membrane – innermost covering of the cell ◦ Cell wall – outside of cell membrane, made up of a special mix of polysaccharides and proteins (antibiotics break it down) ◦ Capsule – outside of the cell wall, protective covering (not all bacteria have it) ◦ Flagella (sing. Flagellum) – long, whiplike structure that moves bacteria ◦ Pili – short, hair-like projection used to stick to other surfaces and for conjugation (exchange of genetic materials between bacteria) ◦ Cytoplasm – jelly-like fluid that dissolves substances and holds organelles ◦ Ribosomes – organelles that make proteins in the cytoplasm http://www.ted.com/talks/lang/eng/bonnie_bassler_on_how_bacteria_communicate.html Protists, Fungi, Plants, and Animals Have nucleus and membrane-bound organelles Much larger and more complex than prokaryotic cells. Reproduce sexually and asexually Nucleus ◦ Control center of cell; contains most of the cell’s DNA Nucleolus ◦ Location where ribosomes are synthesized Nuclear pore ◦ Allows RNA to move in and out of nucleus Ribosomes ◦ Protein synthesis Rough ER ◦ Comprised of a network of tubes and flattened sacs. ◦ Continuous with plasma membrane and nuclear membrane ◦ Site of protein synthesis (consists of ribosomes) Smooth ER ◦ Site of lipid and carbohydrate metabolism ◦ No ribosomes Golgi Apparatus ◦ Connected with ER; flattened disc-shaped sacs, stacked one on top of the other ◦ Modification, storage, and packaging of proteins. ◦ “tags” proteins so they go to the correct destination. Lysosomes (in animal cells and some protists) ◦ Digestion of nutrients, bacteria, and damaged organelles; destruction of certain cells during embryonic development Peroxisomes ◦ Diverse metabolic processes with breakdown of H2O2 by-product Vacuoles ◦ Digestion (like lysosomes); storage of chemicals, cell enlargement; water balance Chloroplasts ◦ Conversion of light energy to chemical energy of sugars (site of photosynthesis) Mitochondria ◦ Conversion of chemical energy of food to chemical energy of ATP ◦ “Power House” of cell ◦ Bound by double membrane Cytoskeleton (including cilia, flagella, and centrioles in animal cells) ◦ Maintenance of cell shape; anchorage for organelles; movement of organelles within cells; cell movement; mechanical transmission of signals from exterior of cell to interior. Cell walls (in plants, fungi, and protists) ◦ Maintenance of cell shape and skeletal support; surface protection; binding of cells in tissues