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Introduction to the Cell.docx

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BIOL 130
Heidi Engelhardt

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Unit 1: Introduction to the Cell KEY TERMS  historical o light microscopy and the discovery of the cell o cell theory o facts, hypotheses, theories and the scientific method o ‘strands’ of cell biology – cytology, biochemistry, genetics  basic properties shared by all cells  classes of cells o prokaryotes - two kingdoms o eukaryotes- membrane-bound compartments, nucleus  endomembrane system – ER, Golgi, lysosomes, vesicles  mitochondria, chloroplasts o origins of eukaryotic cells - endosymbiont theory  cytoskeleton  model organisms in cell biology  Greek/ Latin roots of Cell Biology CELL THEORY HISTORY  Before microscope, it was not known that cells exsisted  Robert Hooke (1635-1703) o first microscope o viewed slices of cork o found “cellula” (little rooms- actually saw cell walls)  Antoni Van Leeuwenhoek (1632-1723) o “father of microbiology” o worked with glass  huge improvement in quality of lenses  nearly 300x magnification became possible o first to observe: (drew what he saw)  single-celled organisms “animalcules”  protists from pond water  bacteria from his mouth  blood cells  banded pattern in muscle cells  sperm  Progress stalled for a century o limited resolving power o emphasis on description rather than explanation (only drawings)  Compound microscope (1830s) o improved magnification and resolution o allowed visualization of objects less than 1 μm  Beginnings of Cell Theory  1833 Robert Brown (botanist) o noticed that every plant cell contained a round structure “kernel” (now known as nucleus)  1838 Matthias Schleiden (another botanist) o all plant tissues are composed of cells o embryonic plant always arose from a single cell  1839 Theodor Schwann (zoologist) o similar observations in animal cells o recognition of structural similarities btw plants and animals! o Cell Theory was formulated (challenged religious and cultural views) CELL THEORY  all organisms consist of one or more cells  the cell is the basic unit of structure for all organisms  all cells arise only from pre-existing cells (added 20 years later) FACTS AND SCIENTIFIC METHOD  fact: o something we know and believe to be true …  fact (scientific): o an attempt to state our best current understanding (based on observations and experiments) o valid only until revised or replaced by a better understanding, based on more careful observations or more discriminating experiments (can be revised)- a fact it only a fact until it is proven to be not true  theory: o a hypothesis that has been tested critically under many different conditions and by many different investigators using a variety of different approaches o by the time an explanation is regarded as a theory it is widely accepted by most scientists in the cell o the “solid ground” of science o evolution, germ theory, cell theory  law: o if a theory is thoroughly tested and confirmed over many years, it becomes a law o gravity, laws of thermodynamics, laws that govern behaviour of gases o biologists are conservative about using the term ‘law’ (revise theories instead)- mainly used in physics  Scientific Method: o make observations o use inductive reasoning to develop tentative explanation (hypothesis) o make predictions based on your hypothesis o make further observations or design and carry out controlled experiments to test your hypothesis o interpret your results to see if they support your hypothesis STRANDS OF CELL BIOLOGY  Biochemistry (synthesis in a lab)  Cytology (looking at cell directly) o Light Microscopy:  Unstained: sperm cells bright field phase contrast DIC  Stained: blood cells small intestine tissue o Fluorescence Microscopy:  Bombard with light of a certain wavelength-  Tag certain proteins in cells with fluorescence (glow when hit with certain wavelengths) o Electron Microscopy- lining of trachea  Scanning Electron Microscope (SEM)- surface scan (used to see interaction with other cells)  Transmission Electron Microscope (TEM)- a ‘slice’ (can see organelles within cells)  Genetics (DNA, chromosomes)  In the 1930’s, these strands combined, which lead to modern advancs such as “dolly” and nanotechnology BASIC PROPERTIES OF CELLS  Cells … o are highly complex and organized  atoms  molecules  macromolecules  (organelles ) enclosed in plasma membrane o use the same ‘genetic program’  Central Dogma (DNA-RNA-protein) o are capable of reproducing themselves  must first replicate genetic material (mitosis and meiosis) o acquire and use energy (“bioenergetics”) and carry out a variety of chemical reactions (“cellular metabolism”) o have many processes that are highly conserved at the molecular level  membrane structure, genetic code, ATP synthesizing enzymes, actin filaments, eukaryotic flagella, … o engage in many mechanical activities  transport of materials in/out, within  assembly and disassembly of structures  motility / movement o respond to environmental signals  move away or toward stimuli  respond to hormones, growth factors, etc o are capable of self-regulatio“homeostasis”  most evident when control systems break down  defects in DNA replication, DNA repair, cell cycle control, …  Two classes of cells: o Prokaryote (before-nucleus)- most diverse (some have flagellum)  No nucleus  ‘naked’ DNA  cell wall in addition to plasma membrane (most)  Eubacteria o cells walls except mycoplasma (smallest) o mycoplasma (simplest) to cyanobacteria (complex)  archaebacteria o all have cell wall o extremophiles  halophiles (Great Salt Lake, Dead Sea)  acidophiles  thermophiles (Taq polymerase- PCR) o eukaryote (true-nucleus)  have nucleus  protisits o very diverse group (don’t have much in common) o mostly single cells, but some colonies o includes algae, water molds, slime molds  fungi o single cells (yeasts) and multicellular (mushrooms- decomposers) o cell walls, heterotrophs  dependent on external source of organic compounds  plants o multicellular o cell wall, chloroplast, vacuole o autotrophs Nuclear envelope Nucleolus Nucleus Chromosom
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