General biology lecture notes copy

General Biology Lecture Notes copy
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Unformatted text preview: General Biology Lecture 1: Chapter 4 Organization of the Cell I. Cell A. smallest unit to carry out all activities associated with life (maintenance, growth, & division) B. Viruses are acellular because they cannot independently perform metabolic activities C. Cell Theory provides consistent explanation for all verifiable data relating to living things 1. Cells are basic units of organization & function in all living organisms 2. All cells come from other cells. All living cells have evolved from a common ancestor II. Cell Organization & Size A. Relationship between cell organization & homeostasis- Cells have many organelles, internal conditions, & have to work constantly to restore & maintain these to enable their biochemical mechanisms to function. 1. homeostasis appropriate internal environment 2. Plasma membrane- surrounds the cell- separates cell from external environment- allows exchange of materials with environment- allows chemical composition of cell to be different from that outside the cell B. Relationship between cell size & homeostasis 1. Measurement-(mm) millimeter = 1/1,000 of meter = 10-3 meter-( m) micrometer = 1/1,000,000 of meter = 10 -6 meter-(nm) nanometer = 1/1,000,000,000 of meter = 10-9 meter-(mm) millimeter = 1/1,000 of meter-( m) micrometer = 1/1,000 of millimeter-(nm) nanometer = 1/1,000 of micrometer 2. Surface to Volume Ratio-ratio of plasma membrane (surface area) to cells volume-regulates passage of material into & out of cell-critical factor in determining cell size-as cell becomes larger, its volume increases at a greater rate than its surface area, decreasing surface-to-volume ratio-a long, thin cell increases ratio & allows it to be more efficient to carry out activities- microvilli, projections of plasma membrane, increase surface area for absorbing nutrients Ex . - Nerve cells need to communicate with each other; have long extensions Ex 2 . Epithelial cells stacked on one another become barrier cell e.g. skin Ex. 3 . Flagella allows sperm to swim III. Methods For Studying Cells A. Microscopes 1. Light microscopes minimal resolution (max is 1,000X) a. Phase contrast light microscope can be used to view stained or living cells, but at relatively low resolution 2. Electron microscope superior resolution power & magnification, since electron beams have very short wavelengths a. Transmission electron microscope (TEM) produces a high-resolution image that can be greatly magnified-looks for a specific reaction-electron beam passes through the specimen-resulting image is a thin cross section of the cell b. Scanning electron microscope (SEM) provides a clear, 3-D view of surface features-Magnification ratio of the size of the image seen to the actual size-Resolution distinguishing of fine detail; minimum distance between 2 points that can be seen separately & clearly-If wavelength decreases, resolution increases B. Cell fractionation-purifies organelles to study function of cell structures...
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