AP Biology 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  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  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 Year Gap???  Between the Hooke/Leuwenhoek discoveries and the mid 19 th 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 19 th 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  German Botanist, Matthias Schleiden, concluded that all plant parts are made of cells  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  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)( )  2. The cell is the basic unit of life in all living things. (Schleiden & Schwann)( )  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 sub- cellular 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:  Disease/Health/Medical Research and Cures(AIDS, Cancer, Vaccines, Cloning, Stem Cell Research, etc.)

It’s all about: Surface Area-to-Volume Ratio Cell radius (r) 1 unit 10 units Surface area (4 ╥ r 2 ) units units 2 Volume(4/3 ╥ r 3 ) units units 3 Large Cells vs. Small Cells Why Are Cells So Small? Size Matters! As a cell get larger, its volume increases at a faster rate than its surface area! SA/V= ______

AP Biology Archaebacteria & Bacteria Classification  Old 5 Kingdom system  Monera, Protists, Plants, Fungi, Animals  New 3 Domain system  reflects a greater understanding of evolution & molecular evidence  Prokaryote: Bacteria  Prokaryote: Archaebacteria  Eukaryotes  Protists  Plants  Fungi  Animals Prokaryote Eukaryote

AP Biology Kingdom Protist Kingdom Fungi Kingdom Plant Kingdom Animal Kingdom Archaebacteria Kingdom Bacteria

AP Biology Prokaryotes Domain Bacteria Domain Archaebacteria Domain Bacteria Domain Archaea Domain Eukarya Common ancestor

AP Biology Bacteria live EVERYWHERE!  Bacteria live in all ecosystems  on plants & animals  in plants & animals  in the soil  in depths of the oceans  in extreme cold  in extreme hot  in extreme salt  on the living  on the dead Microbes always find a way to make a living!

AP Biology Bacterial diversity rods and spheres and spirals… Oh My!

AP Biology Prokaryote Structure  Unicellular  bacilli, cocci, spirilli  Size  1/10 size of eukaryote cell  1 micron (1um)  Internal structure  no internal compartments  no membrane-bound organelles  only ribosomes  circular chromosome, naked DNA  not wrapped around proteins prokaryote cell eukaryote cell

AP Biology Eukaryotes Domain Eukarya Domain Bacteria Domain Archaea Domain Eukarya Common ancestor

AP Biology Eukaryote Structure  Unicellular or Multicellular  Plant, animal, fungi, protist  Size  10X larger than a prokaryote cell  micron (1um)  Internal structure  Far more complex (compartmentalized)  nucleus containing DNA  other membrane-bound organelles  ribosomes (no membrane)  Linear chromosome  wrapped around proteins prokaryote cell eukaryote cell

AP Biology Prokaryote vs. Eukaryote Chromosome double helix Prokaryote Eukaryote

AP Biology Variations in Cell Interior internal membranes for photosynthesis like a chloroplast (thylakoids) internal membranes for respiration like a mitochondrion (cristae) aerobic bacterium mitochondria cyanobacterium (photosythetic) bacterium chloroplast

AP Biology Prokaryote Cell Wall Structure peptide side chains cell wall peptidoglycan plasma membrane protein Gram-positive bacteria Gram-negative bacteria peptidoglycan plasma membrane outer membrane outer membrane of lipopolysaccharides cell wall peptidoglycan = polysaccharides + amino acid chains lipopolysaccharides = lipids + polysaccharides That’s important for your doctor to know!

AP Biology 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  direct transfer of DNA conjugation

AP Biology 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 & B 12 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 =  m = one thousandth of 1 mm.

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.mm common name = Giant Amoeba Chaos diffluens, is an amoeba closely related to the giant amoebaeamoebagiant

AP 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