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rav65819_ch04_059-084 - *58 part II Chapter 4 biology of...

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***58 part II Chapter 4 biology of the cell Cell Structure introduction ALL ORGANISMS ARE COMPOSED OF CELLS. The gossamer wing of a butterfly is a thin sheet of cells and so is the glistening outer layer of your eyes. The hamburger or tomato you eat is composed of cells, and its contents soon become part of your cells. Some organisms consist of a single cell too small to see with the unaided eye, while others, such as humans, are composed of many specialized cells, such as the fibroblast cell shown in the striking fluorescence micrograph on this page. Cells are so much a part of life that we cannot imagine an organism that is not cellular in nature. In this chapter, we take a close look at the internal structure of cells. In chapters 5 to 10, we will focus on cells in action—how they communicate with their environment, grow, and reproduce. concept outline 4.1 Cell Theory n Cell theory is the unifying foundation of cell biology Cell size is limited Microscopes allow visualization of cells and components All cells exhibit basic structural similarities 4.2 Prokaryotic Cells Prokaryotic cells have relatively simple organization Bacterial cell walls consist of peptidoglycan Archaea lack peptidoglycan Some prokaryotes move by means of rotating flagella 4.3 Eukaryotic Cells The nucleus acts as the information center Ribosomes are the cell’s protein synthesis machinery 4.4 The Endomembrane System The rough ER is a site of protein synthesis The smooth ER has multiple roles
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4.5 Mitochondria and Chloroplasts: Cellular Generators The Golgi apparatus sorts and packages proteins Lysosomes contain digestive enzymes Microbodies are a diverse category of organelles Plants use vacuoles for storage and water balance Mitochondria metabolize sugar to generate ATP Chloroplasts use light to generate ATP and sugars Mitochondria and chloroplasts arose by endosymbiosis 4.6 The Cytoskeleton Three types of Fbers compose the cytoskeleton Centrosomes are microtubule-organizing centers The cytoskeleton helps move materials within cells 4.7 Extracellular Structures and Cell Movement Some cells crawl ±lagella and cilia aid movement Plant cell walls provide protection and support Animal cells secrete an extracellular matrix ***59 4.1 Cell Theory A general characteristic of cells is their microscopic size. Although there are exceptions, a typical eukaryotic cell is 10 to 100 micrometers ( m m) (10 to 100 millionths of a meter) in diameter, most prokaryotic cells are only 1 to 10 m m in diameter. Because cells are so small, their discovery did not occur until the invention of the microscope in the seventeenth century. Robert Hooke was the first to observe cells in 1665, naming the shapes he saw in cork cellulae (Latin, “small rooms”). This comes down to us as cells. Another early microscopist, Anton van Leeuwenhoek first observed live cells, which he termed tiny “animalcules.” After these
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rav65819_ch04_059-084 - *58 part II Chapter 4 biology of...

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