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Chapter 2

Chapter 2 origins of life.docx

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York University
BIOL 1000
Nicole Nivillac

Chapter 2 origins of life Cell theory 1) All organisms are composed of one or more cells 2) The cell is the smallest unit that has the properties of life 3) Cells arise only from the growth and division of preexisting cells The origin of the info system - All organism contain DNA - Double stranded helical molecule , contains unique alphabet that provides instructions for assembling many of the important components of a cell organism - DNA is copied onto RNA, which directs the production of protein molecules - Info pathway is preserved form gen to gen - Changes in DNA is what contributes to evolution. The development of energy harnessing reaction pathways - Redox reactions were among the first energy releasing reactions. - Oxidation is loss of electrons. - Reduction is gain of electrons. Early life - Earliest evidence of life found in structures called stromatolites- layered rock that is formed when microorganisms bind particles of sediment together - Prokaryotes have properties common to all cells. - All life forms are based on Prokaryotic(unicell) and eurkaryotic(multi cell) - Prokaryotic are split into two domains:Archaea and Bacteria - All cells have a plasma membrane which separates the env from the cytoplasm - Eukaryotes use mitochondria to create energy - DNA structure is different between Eukaryotes and Prokaryotes - Prokaryotes lack a nucleus, DNA is found in the central region called nucleoid - Prokaryotes are very diverse - Cyanobacteria managed to harness electrons from water instead of hydrogen sulfide, which created oxygen due to photosynthesis. - Oxygenic photosynthesis is more advantageous because water is more abundant than hydrogen sulfide Eukaryotic Cells - DNA and cytoplasm are separated by nuclear envelope - Membrane bound compartments have specialized functions: mitochondria, chloroplasts, endoplasmic reticulum, and golgi complex - Highly specialized motor proteins that move cells and internet cell parts - Functional and structural components called organelles - Endomembrane system Nuclear envelope Seperates cytoplasm and DNA ER Extensive interconnected network or membranous channels and veiscles. Rought ER is layed by ribosomes, creates protein for outside the cell Smooth ER has no ribosomes, creates lipids that become part of cell membrane Golgi complex Stack of flattened membranous sacs, located between rough ER and plasma membrane, modifies proteins
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