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BIOLOGY AND SOCIETY Antibiotics: Drugs that Target Bacterial Cells Chapter 4 Antibiotics were first isolated from mold in 1928. A Tour of the Cell...

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1 Chapter 4 Chapter 4 A Tour of the Cell • Antibiotics were first isolated from mold in 1928. • The widespread use of antibiotics drastically decreased deaths from bacterial infections. • Most antibiotics kill bacteria while minimally harming the human host by binding to structures found only on bacterial cells. – Some antibiotics bind to the bacterial ribosome, leaving human ribosomes unaffected. – Other antibiotics target bacterial enzymes BIOLOGY AND SOCIETY Antibiotics: Drugs that Target Bacterial Cells Figure 4.0 Bordetella pertussis (bacteria) Cilia on human throat cells THE MICROSCOPIC WORLD OF CELLS • Organisms are either – single-celled, such as prokaryotes and most protists or – multicelled, such as plants, animals, and most fungi Microscopes as Windows on the World of Cells Light microscopes can be used to explore the structures and functions of cells. • When scientists examine a specimen on a microscope slide – Light passes through the specimen – Lenses enlarge, or magnify, the image • A photograph taken with a microscope is called a micrograph Light Micrograph (LM) (for viewing living cells) Light micrograph of a protist, Paramecium Fig. 4.1a
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2 Magnification is an increase in the specimen’s apparent size. Resolving power is the ability of an optical instrument to show two objects as separate. – The normal human eye can resolve points as close together as 0.1 millimeter (mm), about the size of a very fine grain of sand – For light microscopes, the resolving power is 0.2 micrometer ( μ m), the size of a small bacterial cell • Cells were first described in 1665 by Robert Hooke. • By the mid-1800s, the accumulation of scientific evidence led to the cell theory . – All living things are composed of cells – The cell is the basic structural and functional unit of a living thing – All cells come from other cells • The electron microscope (EM) uses a beam of electrons, which results in a 100-fold better resolving power than the light microscope. • There are two main kinds Scanning electron microscope (SEM) examines cell surfaces. – Provide 3-dimensional images Transmission electron microscopes (TEM) are useful for internal details of cells. – Provide 2-dimensional images Scanning Electron Micrograph (SEM) (for viewing surface features) Scanning electron micrograph of Paramecium Fig. 4.1b Transmission Electron Micrograph (TEM) (for viewing internal structures) Transmission electron micrograph of Paramecium Fig. 4.1c • The electron microscope can: – Magnify up to 100,000 times – Distinguish objects as small as 0.2 nanometer (nm) • However, preparing a specimen for an electron microscope usually requires killing and preserving the cell with chemicals – Thus, the light microscope is still very useful to view living cells
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Chapter 5 Chapter 5 The Working Cell
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BIOLOGY AND SOCIETY Harnessing Cellular Structures Cells control their chemical environment using energy enzymes, and the plasma membrane Cell-based nanotechnology may be used to power microscopic robots.
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A reflection paper with 2 FULL pages long. Double Space, 12 size TIMES NEW ROMAN. Summarize the main points from Chapter 4&5 and relating to your own life.
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Initially biology was a descriptive science which aimed at studying morphology of living
beings and their systematic arrangement into groups and subgroups based on similarities and

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