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Cell Structure and Function BIOLOGY Chapter 4: pp. 59-84 10th Edition Cell Structure and S. Sylvia Function Plasma membrane: outer surface that Ribosome: Fimbriae: regulates entrance site of protein synthesis hairlike bristles that and exit of molecules allow adhesion to Mader the surfaces Inclusion body: Conjugation pilus: stored nutrients for elongated, hollow later use appendage used for DNA transfer to other Nucleus: Mesosome: bacterial cells plasma membrane Cytoskeleton: maintains cell that folds into the Nucleoid: shape and assists cytoplasm and location of the bacterial movement of increases surface area chromosome cell parts: Endoplasmic Plasma membrane: reticulum: sheath around cytoplasm that regulates entrance and exit of molecules Cell wall: covering that supports, shapes, and protects cell Glycocalyx: gel-like coating outside cell wall; if compact, called a capsule; if diffuse, called a slime layer Flagellum: rotating filament present in some bacteria that pushes the cell forward *not in plant cells PowerPoint® Lecture Slides are prepared by Dr. Isaac Barjis, Biology Instructor 1 Copyright © The McGraw Hill Companies Inc. Permission required for reproduction or display Outline Cellular Level of Organization Cell theory Cell size Prokaryotic Cells Eukaryotic Cells Organelles Nucleus and Ribosome Endomembrane System Other Vesicles and Vacuoles Energy related organelles Cytoskeleton Centrioles, Cilia, and Flagella 2 Cell Theory Detailed study of the cell began in the 1830s A unifying concept in biology Originated from the work of biologists Schleiden and Schwann in 1838-9 States that: All organisms are composed of cells German botanist Matthais Schleiden in 1838 German zoologist Theodor Schwann in 1839 All cells come only from preexisting cells German physician Rudolph Virchow in 1850’s Cells are the smallest structural and functional unit of organisms 3 Organisms and Cells Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. a. c. b. 50 m d. 140 m a: © Geoff Bryant/Photo Researchers, Inc.; b: Courtesy Ray F. Evert/University of Wisconsin Madison; c: © Barbara J. Miller/Biological Photo Service; d: Courtesy O. Sabatakou and E. Xylouri-Frangiadak 4 Sizes of Living Things Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 0.1 nm 1 nm 10 nm 100 nm 1 m 10 m 100 m 1 mm 1 cm 0.1 m 1 m 10 m 100 m 1 km protein chloroplast plant and mouse rose animal frog egg amino cells acid virus ostrich most bacteria human egg ant egg atom blue whale electron microscope human light microscope human eye 5 Cell Size Cells range in size from one millimeter down to one micrometer Cells need a large surface area of plasma membrane to adequately exchange materials. The surface-area-to-volume ratio requires that cells be small Large cells - surface area relative to volume decreases Volume is living cytoplasm, which demands nutrients and produces wastes Cells specialized in absorption utilize membrane modifications such as microvilli to greatly increase surface area per unit volume 6 Surface to Volume Ratio Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. One 4-cm cube Eight 2-cm cubes Sixty-four 1-cm cubes Total surface area (height × width × number of sides × number of cubes) 96 cm2 192 cm2 384 cm2 Total volume (height × width × length × number of cubes) 64 cm3 64 cm3 64 cm3 Surface area: Volume per cube (surface area ÷ volume) 1.5:1 3:1 6:1 7 Microscopy Today: Compound Light Microscope Light passed through specimen Focused by glass lenses Image formed on human retina Max magnification about 1000X Resolves objects separated by 0.2 mm, 500X better than human eye 8 Compound Light Microscope Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 85 µ m amoeba, light micrograph eye ocular lens light rays objective lens specimen condenser lens light source a. Compound light microscope © Robert Brons/Biological Photo Service 9 Microscopy Today: Transmission Electron Microscope Abbreviated T.E.M. Electrons passed through specimen Focused by magnetic lenses Image formed on fluorescent screen Similar to TV screen Image is then photographed Max magnification 1000,000sX Resolves objects separated by 0.00002 mm, 100,000X better than human eye 10 Transmission Electron Microscope Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 200 nm pseudopod segment, transmission electron micrograph electron source electron beam electromagnetic condenser lens specimen electromagnetic objective lens electromagnetic projector lens observation screen or photographic plate b. Transmission electron microscope © M. Schliwa/Visuals Unlimited 11 Microscopy Today: Scanning Electron Microscope Abbreviated S.E.M. Specimen sprayed with thin coat of metal Electron beam scanned across surface of specimen Metal emits secondary electrons Emitted electrons focused by magnetic lenses Image formed on fluorescent screen Similar to TV screen Image is then photographed 12 Scanning Electron Microscope Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 500 µ m amoeba, scanning electron micrograph electron gun electron beam electromagnetic condenser lenses scanning coil final condenser electron lens detector secondary electrons TV specimen viewing screen c. Scanning electron microscope © Kessel/Shih/Peter Arnold, Inc. 13 Microscopy Today: Immunofluorescence Light Microscope Antibodies developed against a specific protein Fluorescent dye molecule attached to antibody molecules Specimen exposed to fluorescent antibodies Ultra-violet light (black light) passed through specimen Fluorescent dye glows in color where antigen is located Emitted light is focused by glass lenses onto human retina Allows mapping distribution of a specific protein in cell 14 Microscopy Today: Confocal Microscopy Narrow laser beam scanned across transparent specimen Beam is focused at a very thin plane Allows microscopist to optically section a specimen Sections made at different levels Allows assembly of 3d image on computer screen that can be rotated 15 Microscopy and Amoeba proteus Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 85 µ m 200 nm 500 µ m amoeba, light micrograph pseudopod segment, transmission electron amoeba, scanning electron micrograph micrograph electron source electron gun eye electron beam ocular lens electron beam light rays electromagnetic condenser lens electromagnetic condenserl enses specimen electromagnetic objective lens objective lens scanning coil specimen condenser lens final electromagnetic Condenser electron projector lens lens detector secondary observation screen electrons TV or specimen Viewing light source photographic plate screen a. Compound light microscope b. Transmission electron microscope c. Scanning electron microscope a: © Robert Brons/Biological Photo Service; b: © M. Schliwa/Visuals Unlimited; c: © Kessel/Shih/Peter Arnold, Inc. 16 Microscopy and Cheek Cells Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 30 m 30 m 25 m 25 m 25 m Bright-field. Light Bright-field (stained). Differential interference Phase contrast. Density Dark-field. Light is passed passing through the Dyes are used to stain contrast. Optical methods differences in the through the specimen at specimen is brought the specimen. Certain are used to enhance specimen cause light rays an oblique angle so that directly into focus. Usually, components take up density differences within to come out of “phase.” the objective lens receives the low level of contrast the dye more than other the specimen so that The microscope enhances only light diffracted and within the specimen components, and therefore certain regions appear these phase differences so scattered by the object. interferes with viewing all contrast is enhanced. brighter than others. This that some regions of the This technique is used to but its largest components. technique is used to view specimen appear brighter view organelles, which living cells, chromosomes, or darker than others. The appear quite bright against and organelle masses. technique is widely used a dark field. to observe living cells and organelles. (Bright field): © Ed Reschke; (Bright field stained): © Biophoto Associates/Photo Researchers, Inc.; (Differential, Phase contrast, Dark field): © David M. Phillips/Visuals Unlimited 17 Prokaryotic Cells Lack a membrane-bound nucleus Structurally smaller and simpler than eukaryotic cells (which have a nucleus). Prokaryotic cells are placed in two taxonomic domains: Bacteria Archaea Live in extreme habitats Domains are structurally similar but biochemically different 18 The Structure of Bacteria Extremely small - 1–1.5 μm wide and 2–6 μm long Occur in three basic shapes: Spherical coccus, Rod-shaped bacillus, Spiral spirillum (if rigid) or spirochete (if flexible). Cell Envelope includes: Plasma membrane - lipid bilayer with imbedded and peripheral protein Form internal pouches (mesosomes) Cell wall - maintains the shape of the cell and is strengthened by peptidoglycan Glycocalyx - layer of polysaccharides on the outside of the cell wall Well organized and resistant to removal (capsule) 19 The Structure of Bacteria Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. spirillum spirochete bacillus coccus 20 The Structure
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