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Chapter 3

BIOL 1000 Chapter 3 - Defining Life and Its Origins.docx

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BIOL 1000
Jennifer Steeves

Chapter 3 – Defining Life and its Origins 3.3 – From Macromolecules to Life • Early Metabolism was probably based on simple oxidation-reduction reactions 3.4 – The Earliest Forms of Life • Some early cells developed the capacity to carry out photosynthesis • The oxygen produced as a by-product accumulated  Oxidising character of Earth’s atmosphere increased • From this time on, organic molecules produced in the environment were quickly broken down  Life could only arise from pre-existing life; as it is today • We are all (Bacteria, Archaea, Eukarya) descended from LUCA  Last Universal Common Ancestor • All Life-forms on Earth share a set of common characteristics: 1. Cells made of lipid molecules brought together forming a bilayer 2. A genetic system based on DNA (universal) 3. A system of information transfer; DNA-RNA-Protein (Central Dogma) 4. System of Protein assembly; Transcription-Translation 5. Reliance on proteins as the major structural and catalytic molecule 6. Use of ATP as the molecule of chemical energy 7. Usage of Glycolysis to generate ATP Why is Carbon Necessary? • Carbon is the backbone/basis of all organic molecules in existence • Organisms are constantly producing these organic molecules to keep them running Obtaining Carbon • Heterotrophs – Obtain organic carbon by consuming other organisms • Autotrophs – Synthesize organic carbon molecules using inorganic carbon, CO2 Obtaining Energy • Phototrophs – use light as a source of energy for photosynthesis • Chemotrophs – Oxidation of organic or inorganic substances 3.5 – The Eukaryotic Cell and the Rise of Multicellularity • The energy-transducing organelles (chloroplast and mitochondria) are thought to have derived from free-living prokaryotic cells • Theory of Endosymbiosis – Mitochondria developed from ingested aerobic bacteria; chloroplast developed from ingested cyanobacteria • Following Endosymbiosis, genes residing in these two organelles moved to the nucleus; HGT  Horizontal Gene Transfer - The transfer of genes between organisms in a manner other than traditional reproduction • Eukaryotic cells are more complex because mitochondria provide them with more energy • Multicellular Eukaryotes probably evolved by differentiation of cells of the same species that had congregated into colonies  Evolved several times, producing lineages of several algae and ancestors of fungi, plants, and animals Endomembrane System - Eukaryotes • Probably evolved from the infolding of the Plasma Membrane • Consists of – Nuclear Envelope, Endoplasmic Reticulum, and The Golgi Complex Evolution Domains 1. Bacteria – E.g. E. coli  Prokaryote  Circular DNA within nucleoid (chromosomal region)
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