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Unformatted text preview: Biology Notes Section 4: Lecture 5 + Chapter 4 Cells- the smallest independent units of life Cell Theory: That cells are the basic units of structure in all living things; put forth by Schleiden, Schwann, and Virchow in the mid-19 th century. History: - 1665: Robert Hooke named cells after monks cells because of their appearance. - Late 1600s: Leeuwenhoek used primitive microscopes to show that there existed living things on a level we cannot see with the naked eye. - 1839: Schwann imaged the frog cartilage at a cellular level. - When the egg cell was discovered it was thought that it contained a homunculus; when sperm cells were discovered later on, there arose a debate btw ovists and spermists as to which cell housed the homunculus. - 1890s: There was a solution to the debate about whether there is one neuron w/ many processes (previously believed) or if there are several independent neurons that interact with each other ( Neuron Doctrine) . *Not necessarily accepted by all: o Ramon y Cajal proved the Neuron Doctrine using Golgis cell staining method; Golgi himself, however, was unconvinced of the new doctrine. Microscopes and sizes: Resolution levels of microscopes, low to high = light transmission electron scanning electron. Size comparisons: - 1 cm = 1/100 meter - 1 mm = 1/1000 meter - 1 micrometer (micron) = 1/1,000,000 meter - 1 nanometer (nm) = 1/1,000,000,000 meter Larger organisms have more cells, not larger cells. Why? Because of Surface to Volume Ratios: - Amt of oxygen a cell can take in, and amt of waste it produces, depend on its surface area. - The more volume it has the more oxygen it needs and the more waste it produces. - BUT: volume increases by the cube of the linear proportions and surface area by the square. o Thus, as cells get bigger, the surface to volume ratio drops , so a cell will not be able to take in enough oxygen or properly dispose of its waste. - For this reason, tumors must get vascular system support as they grow in order to survive. Prokaryotic cell structure: - No nucleus; their DNA is clumped together in the cell, unbound in an area called nucleoid....
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