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Transcript
The Cell Theory AP Biology Some Random Cell Facts The average human being is composed of around 100 Trillion individual cells!!! It would take as many as 50 cells to cover the area of a dot on the letter “i” WOW!!! AP Biology Discovery of Cells 1665- English Scientist, Robert Hooke, discovered cells while looking at a thin slice of cork. He described the cells as tiny boxes or a honeycomb He thought that cells only existed in plants and fungi AP Biology Anton van Leuwenhoek 1673- Used a handmade microscope to observe pond scum & discovered single-celled organisms He called them “animalcules” He also observed blood cells from fish, birds, frogs, dogs, and humans Therefore, it was known that cells are found in animals as well as plants AP Biology 150-200 Year Gap??? Between the Hooke/Leuwenhoek discoveries and the mid 19th century, very little cell advancements were made. This is probably due to the widely accepted, traditional belief in Spontaneous Generation. Examples: -Mice from dirty clothes/corn husks -Maggots from rotting meat AP Biology 19th Century Advancement Much doubt existed around Spontaneous Generation Conclusively disproved by Louis Pasteur Pasteur: Ummm, I don’t think so!!! ? = + AP Biology Development of Cell Theory 1838- German Botanist, Matthias Schleiden, concluded that all plant parts are made of cells 1839- German physiologist, Theodor Schwann, who was a close friend of Schleiden, stated that all animal tissues are composed of cells. AP Biology Development of Cell Theory 1858- Rudolf Virchow, German physician, after extensive study of cellular pathology, concluded that cells must arise from preexisting cells. AP Biology The Cell Theory Complete The 3 Basic Components of the Cell Theory were now complete: 1. All organisms are composed of one or more cells. (Schleiden & Schwann)(1838-39) 2. The cell is the basic unit of life in all living things. (Schleiden & Schwann)(1838-39) 3. All cells are produced by the division of preexisting cells. (Virchow)(1858) AP Biology Modern Cell Theory Modern Cell Theory contains 4 statements, in addition to the original Cell Theory: The cell contains hereditary information(DNA) which is passed on from cell to cell during cell division. All cells are basically the same in chemical composition and metabolic activities. All basic chemical & physiological functions are carried out inside the cells.(movement, digestion,etc) Cell activity depends on the activities of subcellular structures within the cell(organelles, nucleus, plasma membrane) AP Biology How Has The Cell Theory Been Used? The basic discovered truths about cells, listed in the Cell Theory, are the basis for things such as: AP Biology Disease/Health/Medical Research and Cures(AIDS, Cancer, Vaccines, Cloning, Stem Cell Research, etc.) Why Are Cells So Small? Size Matters! It’s all about: Surface Area-to-Volume Ratio Large Cells vs. Small Cells Cell radius (r) 1 unit 10 units Surface area (4╥r2) 12.57 units2 1257 units2 ______ Volume (4/3╥r3) 4.189 units3 4189 units3 ______ SA/V= 2.98 0.30 As a cell get larger, its volume increases at a faster rate than its surface area! Eukaryote Classification Old 5 Kingdom system Prokaryote Monera, Protists, Plants, Fungi, Animals New 3 Domain system reflects a greater understanding of evolution & molecular evidence Prokaryote: Bacteria Prokaryote: Archaebacteria Eukaryotes AP Biology Protists Plants Fungi Animals Archaebacteria & Bacteria Kingdom Bacteria Kingdom AP BiologyFungi Kingdom Archaebacteria Kingdom Protist Kingdom Plant Kingdom Animal Prokaryotes Domain Bacteria Domain Archaebacteria Domain Bacteria AP Biology Domain Archaea Domain Eukarya 2007-2008 Common ancestor Bacteria live EVERYWHERE! Bacteria live in all ecosystems on plants & animals in plants & animals in the soil in depths of the oceans Microbes always in extreme cold find a way to make a living! in extreme hot in extreme salt on the living on the dead AP Biology Bacterial diversity rods and spheres and spirals… Oh My! AP Biology eukaryote cell Prokaryote Structure Unicellular prokaryote cell bacilli, cocci, spirilli Size 1/10 size of eukaryote cell 1 micron (1um) Internal structure no internal compartments no membrane-bound organelles only ribosomes AP Biology circular chromosome, naked DNA not wrapped around proteins Eukaryotes Domain Eukarya Domain Bacteria AP Biology Domain Archaea Domain Eukarya 2007-2008 Common ancestor eukaryote cell Eukaryote Structure Unicellular or Multicellular prokaryote cell Plant, animal, fungi, protist Size 10X larger than a prokaryote cell 10-100 micron (1um) Internal structure AP Biology Far more complex (compartmentalized) nucleus containing DNA other membrane-bound organelles ribosomes (no membrane) Linear chromosome wrapped around proteins Prokaryote vs. Eukaryote Chromosome Prokaryote Eukaryote double helix AP Biology mitochondria Variations in Cell Interior cyanobacterium (photosythetic) bacterium chloroplast AP Biology aerobic bacterium Prokaryote Cell Wall Structure Gram-positive bacteria peptide side chains cell wall peptidoglycan plasma membrane That’s important for your doctor to know! protein peptidoglycan = polysaccharides + amino acid chains lipopolysaccharides = lipids + polysaccharides Gram-negative bacteria cell wall outer membrane of lipopolysaccharides outer membrane peptidoglycan AP Biology plasma membrane Prokaryotic metabolism How do bacteria acquire their energy & nutrients? photoautotrophs photosynthetic bacteria chemoautotrophs oxidize inorganic compounds nitrogen, sulfur, hydrogen… heterotrophs live on plant & animal matter decomposers & pathogens AP Biology Genetic variation in bacteria Mutations bacteria can reproduce every 20 minutes binary fission error rate in copying DNA 1 in every 200 bacteria has a mutation you have billions of E. coli in your gut! lots of mutation potential! Genetic recombination bacteria swap genes plasmids small supplemental circles of DNA conjugation AP Biology conjugation direct transfer of DNA Bacteria as pathogens Disease-causing microbes plant diseases wilts, fruit rot, blights animal diseases tooth decay, ulcers anthrax, botulism plague, leprosy, “flesh-eating” disease STDs: gonorrhea, chlamydia typhoid, cholera TB, pneumonia lyme disease AP Biology Bacteria as beneficial (& necessary) Life on Earth is dependent on bacteria decomposers recycling of nutrients from dead to living nitrogen fixation only organisms that can fix N from atmosphere needed for synthesis of proteins & nucleic acids plant root nodules help in digestion (E. coli) digest cellulose for herbivores cellulase enzyme produce vitamins K & B12 for humans produce foods & medicines from yogurt to insulin AP Biology How big are cells? Microscopic (mostly) Measured in microns µm (micrometers) . A µm is one millionth of a meter = 10-9 m = one thousandth of AP Biology How big are cells? Smallest free-living cell = Mycoplasma genitalium Size = 0.2 to 0.3 µm AP Biology How big are cells? Bacteria e.g. Eschericia coli (aka E.coli) Size=1 µm by 3 µm AP Biology How big are cells? Human red blood cell = 8 µm in diameter AP Biology How big are cells? Largest cell on the human body = ovum Size= 1000 µm in diameter (1 mm) AP Biology How big are cells? Smallest cell in the human body = sperm cell. AP Biology How big are cells? Largest cell with a metabolism = Chaos chaos Size=1-5 mm in length. common name = Giant Amoeba osAP diffluens, is an amoeba closely related to the giant amoebae Biology How big are cells? Largest cell = yolk of an ostrich egg AP Biology Ostrich, egg, humans AP Biology Ostrich emerged from egg AP Biology How can we study cells? Problem: They are microscopic! Solution: Use a microscope! AP Biology Types of Microscopes 1. Compound light microscope Light passes through lenses to magnify image up to 1000X Can observe living cells AP Biology Types of Microscopes 2. Electron microscope Uses a beam of electrons to magnify image > 1000X Kills cells being observed AP Biology