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BIO240H Lecture 1.doc

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Jennifer Harris

Lecture 1 Intro to Cells & Nucleic Acids Tree of Life – share similar things (DNA, RNA, proteins) - Composed of 3 major kingdoms: Procaryotes o Bacteria (Eubacteria) – true/normal bacteria Composed of o Archaea (archaebacteria) – characteristics of eubacteria & eucaryotes, grow unicellular in diverse places (thermal places, sewage pits, salt marshes, high acid, low organisms places) o Eucaryotes – multicellular (vertebrates, invertebrates, plants, humans) or single-celled (protists) 2 main types of cells: 1) Procaryotic cells - No nuclei - Single-celled (mostly exist as independent individuals, known to form colonies/communities) - Bacteria & archaea 2) Eucaryotic cells - Nuclei (nucleic acids are separated by nuclear membrane) - Multicellular (not always) - Plants, fungi, animals, humans Procaryotic cells - Very simple cell, not many specialized compartments - Plasma membrane – serves as filter to separate inside from outside & mediate what diffuses in/out - Nucleiod – nucleic acids that are not enclosed by any sort of membrane - Cell wall – protects bacteria from outside - Ribosomes – sites of protein synthesis & free-floating in cytosol. Eukaryotic Cell - Much more complex & divided into many different types of specialized compartments. - Larger (though not always) - Much greater degree of complexity requires structural elements called cytoskeleton which mediate division of cell into specialized compartments, mediate shape cell can have, movements of cell towards things. - Microtubule – help move different organs & proteins up/down these structures. - DNA – contained w/in nuclear envelope. - Ribosomes – tend to be organized into structure called endoplasmic reticulum although some occur in cytosol. - Energy-producing units are contained in mitochondria which produce ATP – site where O is used to oxidize food to produce ATP which is energy currency of cell. Origins of Mitochondria - How does such complex cellular structure evolve? - When O became present, bacterium was able to synthesize O. Mitochondria – use O to make ATP – symbiotic relationship with ancestral eucaryotic cell. - 1 theory of origin of eucaryotic cell: may have come from ancient symbiotic event that would have occurred 1.5 billion years ago when O became plentiful. In beginning, there may have been eucaryotic ancestor that was anaerobic – made its living off of eating free-living aerobic bacteria that were able
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