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Notes on Cells The Origins of Cell Study Individual cells are so small; they are seen in detail only with a microscope. The Origins of Cell Study 1. 1600’s: Leuwenhoek: Dutch, first to magnify nature with a lens It was really just a piece of glass. 2. 1665: Hooke: British, -first to use a compound scope to look at magnified plant tissue (cork); -named cells = basic unit of all life forms 1838: Schleiden: German, (botanist) said all plants were made of cells 4. 1839: Schwann: German, (zoologist) said all animals were made of cells Cell theory: summary of these discoveries a. All living things are made up of cells b. Cells are the basic unit of structure and function in living things c. New cells are produced from existing cells Microscopes Magnification – the power to increase an object’s apparent size Resolution – the power to show detail clearly Magnifying glass – simple microscope Dissecting Microscope Light microscope – uses light Specimen – is the object being viewed Must be thin enough to let light through Compound light microscope – 2 kinds of lenses 1. Ocular – (eyepiece 10x) 2. Objective lens – (near the specimen) Degree of magnification – determined by the lenses x – stands for times Total magnification – multiply the power of the objective by the power of the ocular x Objective *Scan *Low *High *Oil Immersion Power of Ocular objective Total Magnification 4 10 40 10 10 100 40 10 400 100 10 1000 * objectives used in this class How do you increase magnification? Use a 20x ocular • 2000x is usually as high a magnification as can be obtained with a compound microscope Why is 2000x the limit for a compound microscope? Above 2000x – decreased resolution • magnification is no good if clarity (resolution) is lost Above 2000x - you must have an electron microscope • Transmission Electron Microscope (TEM) • Scanning Electron Microscope (SEM) • insect wing To see more microscopy images, click here. Parts of the Light Microscope ocular arm coarse adjustment fine adjustment light source base stage diaphragm stage clips low power objective high power objective Scan objective revolving nosepiece Cell Types Prokaryotic – no true nucleus • no membrane-bound organelles pro = before karyo (Greek) = “nut” or “kernel” nuclei (Latin) = “a little nut” • smaller • no nuclei • have cell membranes and cytoplasm • grow, reproduce, respond to changes in environment Ex. Kingdoms Archaebacteria & Eubacteria bacteria blue-green bacteria (cyanobacteria) Eukaryotic – true nucleus eu = true • do contain nuclei – a structure that contains genetic material and controls cell activities • have cell membrane – thin, flexible barrier around cells • have cytoplasm-material inside cell membrane but not including nucleus Ex. 4 other kingdoms Protista Fungi Plantae Animalia Where do viruses go? Viruses: Are particles of nucleic acid, protein, and in some cases lipids that can reproduce ONLY by infecting living cells. Viruses are made of a core of either DNA or RNA surrounded by a protein coat - capsid. These are T4 Bacteriophages A bacteriophage is a virus which infects bacteria Viruses are not considered alive because they don’t have ALL the characteristics of life. Example: They can’t reproduce independently These are the Influenza Viruses Influenza or "flu" is an infection of the respiratory tract that can affect millions of people every year. The protein in the capsid “tricks” the host cell into allowing the virus inside • once inside it takes over, putting the genetic program of the virus into effect Common diseases caused by viruses: Polio, measles, AIDS, mumps, influenza, yellow fever, rabies, common cold, cancer Scaled Comparison So how do prokaryotes, eukaryotes viruses compare in size? Click here for an interactive demonstration. What kind of scope would you need in order to see: Scaled Comparison What kind of scope would you use to view: • Human cells? LM • Other eukaryotic cells? LM • Prokaryotic cells? LM, oil immersion • Details of intracellular structures? SEM or TEM • Viruses? SEM or TEM only Notes on Cell structures Cytoplasm • jelly-like material inside the cell membrane which contains water, salts, and organic molecules • in constant motion – cytoplasmic streaming http://www.vcbio.science.ru.nl/eng/image-gallery/show/Fi002/gif • surrounds organelles Organelles – specialized structures that perform important cellular functions 1. mitochondria • “powerhouses” • respiration centers for the release of energy • use energy (food molecules) to make high-energy compounds that the cell can use to power growth, development, movement • ATP (adenosine triphosphate) – most prevalent macromolecule in cells that use a lot of energy (muscles) • ATP is generated by mitochondria • enclosed by 2 membranes outer – smooth, form boundary Inner – long folds (cristae) increase surface area 2. endoplasmic reticulum (ER) • membrane system of sacs and tunnels • covered with ribosomes – rough ER, place where proteins are modified • few or no ribosomes – smooth ER, contains enzymes that perform specialized tasks, like production of lipids • “intracellular highway” 3. ribosomes • “protein factories” • made of RNA and proteins • where proteins are made (most numerous organelle) – produces proteins following coded instructions that come from the nucleus • granulated, attached to ER or float in cytoplasm 4. Golgi apparatus • processing, packaging and secreting organelle • stack of membranes or sacs which package proteins produced by rough ER • “protein packagers” 5. Lysosomes • contain digestive enzymes • breakdown carbohydrates, lipids, and proteins into particles that can be used by the cell • breakdown organelles that are no longer useful • remove debris that otherwise accumulates/clutters the cell • in animal cells and fungi • “suicide sacs” lysis = breakdown soma = body 6. Centrioles • rod-shaped bodies close to the nucleus which guides the cell during division • animal cells only 7. Vacuoles • cavities (containers) which store enzymes, waste products, water, salts, proteins, and carbohydrates • mainly in plant cells – plants have a large central vacuole filled with liquid • in mature plants – the vacuole takes up 90% of the volume of the cell • smaller vacuoles are called vesicles 8. Plastids • chemical factories to store food • only in plants • can contain pigments example - chloroplasts Cytoskeleton: framework of cell (supports the cell) • network of protein filaments • used in cell movement 9. microtubules • small hollow tubes of protein; maintains cell shape, forms tracks along which organelles are moved • assembled and broken down as needed (during cell division) • in some cells they form cilia and flagella that aid in movement • act as “bones” in the cell 10. Microfilaments • protein threads of actin for cytoplasmic streaming • smaller than microtubules • act as “muscles” in the cell Nucleus – identified in 1831 • control center of the cell • site of nucleic acid synthesis 1. nuclear envelope (membrane) • double membrane (phospholipids and proteins) • nuclear pores allow substances to enter and leave 2. nucleoplasm • protoplasm within the nucleus • dense, protein rich 3. nucleolus (singular), nucleoli (plural) • form ribosomes • composed of RNA 4. chromatin • fine strands of DNA and proteins • genetic material • chromosomes – coiled up chromatin when the cell is dividing Differences in Plant Cells vs. Animals: a. Cell wall – provides support and protection for the plant cell • contain pores which allow H2O, CO2, and O2 to pass through • made from fibers of carbohydrates and proteins (cellulose) • cellulose – tough carbohydrate fibers, makes up wood and paper b. vacuoles – one large central vacuole • 90% of cell’s volume c. plastids Plastids chloroplast Pigment Function chlorophyll absorb sun’s energy carotene (orange) chromoplast leucoplast xanthophyll (pale yellow) ------ store pigments store food as starches, lipids, or proteins Cell membrane • forms outer boundary and separates the cell from its surroundings and other cells • composed of 2 layers of phospholipids and proteins – both move like a liquid called “fluid mosaic model” • contains protein molecules that provide attachment point for carbohydrate molecules to form chains • some proteins in cell membrane form channels and pumps to help move materials • regulates what enters and leaves the cell – selectively permeable (semipermeable) (Keeps out some molecules but allows others to enter) Endosymbiotic Theory • Endosymbiotic Theory proposes that eukaryotic cells arose from living communities formed by prokaryotic organisms. • Endo- means inside • -symbiotic means living together (relationship) Endosymbiotic Theory • Prokaryotes entered ancestral eukaryotes • Prokaryotes did NOT act as a parasite by infecting the host (eukaryote) • Eukaryotes did NOT digest the prokaryotes • Instead, the smaller prokaryotes began LIVING inside the larger cell – giving rise to eukaryotes Endosymbiotic Theory • 1st - Mitochondria & Chloroplasts have DNA similar to bacterial DNA. • 2nd – Mitochondria & Chloroplasts have ribosomes whose size & structure resembles those of bacteria. • 3rd – Like bacteria, Mitochondria & Chloroplasts reproduce by binary fission when the cells containing them divide by mitosis. Click Here For Animation Tutorial Endosymbiotic Theory • Lynn Margulis Explains Endosymbiotic Theory