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BIOL 141 Chapter 4 Cell Structure OUTLINE

BIOL 141 Chapter 4 Cell Structure OUTLINE - Chapter 4 Cell...

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Chapter 4 . Cell structure 1. Cells a. Discovery b. Surface to Volume ratio c. Cell Theory 2. Prokaryotic cells a. Inside a prokaryotic cell 3. Eukaryotic cells a. Nucleus b. Endomembrane system c. Ribosome d. Mitochondria e. Chloroplast f. Lysosome/Peroxisomes g. Cytoskeleton 4. Cell movement 5. Unique feature of Plant cells a. Cell walls b. Large vacuole -What is in a typical cell? -What do all cells have in common? Three things all cells share : 1. Plasma membrane : Lipid bilayer that surrounds cell 2. Nucleiod or nucleus : Contains genetic material (DNA) 3. Cytoplasm : Semi-fluid matrix that fills the interior of the cell -In eukaryotic cells you have organelles. Organelles are specialized membrane bound compartments. -How big are typical cells? Most are microscopic. First described by Robert Hooke in 1665. He looked at cork (bark from a cork tree) under a microscope and saw small empty chambers; he called these structures cellulae , which is Latin for little room. -Antoine van Leeuwenhoek was the first to describe living cells a few years later. Leeuwenhoek was a Dutch fabric merchant who had little if any scientific training. He got his hands on a microscope and starting look at things microscopically. He was the first to discover bacteria, several protists, nematodes (round worms), rotifers, blood cells and sperm cells. -The importance of the discovery of cells was realized until in 1830’s, about 150 years after Leeuwenhoek. The Cell Theory -In 1838 a botanist name Matthias Schleiden , made careful studies of plant tissues and developed the first modern cell theory. In 1839 Theodore Schwann , made similar studies using animal cells. Three principles of the modern cell theory 1. All organism are composed of one of more cells, and metabolism and heredity occur within these cells 2. Cells are the smallest living things, they are the basic units of organization of all organisms 3. Cells arise only by the division of previously existing cells, basically this means that life only started once, life represents as continuous line from the earliest cells 1
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Why are cells microscopic, why aren’t they larger? -There are some very practical reasons why cells are small. -Communication is perhaps the most important reason; cells need to communicate with each other to function properly. This is easier if the cells are smaller. -Also cells synthesize all kids of stuff, most of it travels by diffusion, diffusion is much faster over short distances. The larger the cell is, the longer it takes for things to diffuse around the cell, and this gives many small cells an advantage of fewer larger cells. Surface to volume ratio -A cells surface (plasma membrane) provides to only opportunity to interact with the environment. - Look at formulas, for a sphere - Surface area = 4 π r 2 - Volume = 4 π r 3 /3 *Example with numbers r = 3 surface area = 113 volume = 113 surface to volume ratio: 1 r = 5 surface area = 315 volume = 529 surface to volume ratio: 0.59 r = 10 surface area = 1256 volume = 4188 surface to volume ratio: 0.29
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