bio- chap 7 - I The Study of Cells A Microscopes 1...

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I. The Study of Cells A. Microscopes 1. evolution of science parallels evolution of technology a. 17 th century- progression in microscope devlopment 2. Light Microscopes (LMs) a. first used by Renaissance artists b. visible light passes thru specimen and then thru glass lens. Lenses refract light so image is magnified 3. Microscopy a. Magnification b. Resolving Power- measure of the clarity of the image; it is the minimum distance two points can be separated and still be distinguished as two separate points - limited by the wavelength of the light 4. Electron Microscope (EM) a. instead of visible light, focuses a beam of electrons though the specimen b. unveil ultrastructure of cell c. shorter wavelenght d. Transmission Electron Microscope (TEM) - aims electron beam thru a thin section of specimen - electromagnets aslenses to focus and magnify cells - internal ultrastructure of cells e. Scanning Electron Microscope (SEM) - detiled study of cell surface - beam excites electrons on surface- reveal topography of specimen - specimen appears 3D B. Cell Fractionation 1. to take cells apart, and separate major organelles so that their individual function can be studied 2. ultracentrifuges use principle of gravity 3. Homogenization a. disruption of cells b. break apart cells without damaging organelles c. in centrifuge, larger heavier parts of cell settle at bottom with smaller and lighterparts at the top d. supernatant separated and process repeated to divide components further and further 4. enables researcher to prepare specific components of cells in bulk quantity in oder to study their composition and functions II. Panoramic View of the Cell A. Prokaryotic Cells 1. bacteria and archaea 2. has no nucleus
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3. genetic matierla conventrated in nucleoid but not separated by a membrane from rest of cell B. Eukaryotic Cell 1. protists, plants, fungi, animals 2. has true nucleus that is separated from rest of cell by a membraneous nuclear envelope 3. cytoplasm is the entire region between nucleus and membrane surrounding cell 4. cytoplasm composed of cytosol- a semifluid medium which contains organeeles of specialized form and function (usually absent in prokaryotic cells) C. Cell Size 1. smallest cells are mycoplasms (bacteria) 2. metabolic requirements impose upper limits on the size that is practical for the cell a. as an object of a particular shape increases in size, its volume grows proportionately more than its surface area b. smaller the object, the greater ratio between surface area and volume 3. Plasma Membrane a. selective barrier to service the entire volume of the cell D. Internal Membrane compartmentalizes the function of eukaryotic cell 1. compartments participate directly in cell’s metabolism 2. many enzymes built right into membs 3. double layer of phospholipids and other lipids a. in bilayer or attached to its surfaces are diverse proteins b. each memb has unique composition of lipids and proteins suited to specific functions III. Nucleus A. contains most of the genes that control the cell
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bio- chap 7 - I The Study of Cells A Microscopes 1...

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