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General Biology Lecture Notes copy

General Biology Lecture Notes copy - General Biology...

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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 μ -6 meter -(nm) nanometer = 1/1,000,000,000 of meter = 10 -9 meter -(mm) millimeter = 1/1,000 of meter -( m) μ 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 cell’s 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
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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 -can be studied in isolated environment a. Centrifugation – Due to centrifugal force, large or very dense particles move
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