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ASTR-3040: Astrobiology

ASTR-3040: Astrobiology. The Nature of Life on Earth Chapter 5. Day 11. Homework - 4. Due Tues. Feb. 22 Chapter 5: 4, 6, 14, 20, 25, 27, 33, 37, 42, 47, 48, 49, 51. Molecular Components. Carbohydrates – energy sources Sugars and starches Lipids – energy stores, barriers Fats

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ASTR-3040: Astrobiology

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  1. ASTR-3040: Astrobiology The Nature of Life on Earth Chapter 5 Day 11

  2. Homework - 4 • Due Tues. Feb. 22 • Chapter 5: • 4, 6, 14, 20, 25, 27, 33, 37, 42, 47, 48, 49, 51

  3. Molecular Components • Carbohydrates – energy sources • Sugars and starches • Lipids – energy stores, barriers • Fats • Nucleic Acids – DNA and RNA

  4. Molecular Components • Proteins – structure & chemistry • Structural materials • Enzymes – catalysts for reactions • Amino Acids (20 used in most life forms)‏ • Left-handed in biological entities.

  5. Major Groupings • Leeuwenhoek – 1674 – microscope • 5 Kingdoms • Plants • Animals • Protista • Monera • Fungi • Is there a biochemical classification?

  6. Microscopic Life • Plants and Animals are different • Cell walls (plants)‏ • Cell Nucleus • Prokaryotes • Eukaryotes All prokaryotes are single celled. They lack a cell nucleus. Eukaryotes – single or multi-celled.

  7. Domains of Life • Based on biochemistry and genetics: • Bacteria • Archaea • Eukarya Tree of life. Kingdom – Phylum – Class – Order – Family – Genus – Species

  8. The Tree of Life • Extremely valuable organizational tool. • 3 key ideas • 1. Domains based on biochemistry & genetics is fundamentally different from the older KPCOFGS based on structural & physiological differences. • 2. New and fundamentally different view of microbes - lipid structure of cell membranes. • 3. True diversity almost entirely in microbes.

  9. Metabolism: Chemistry of Life • Metabolic needs: • 1. Source of raw materials. • 2. Source of energy. • ATP: adenosine triphosphate • Used by every living cell for internal energy. • Outside energy needed only to produce ATP. • Carbon sources – form basic materials. • Energy sources – run the metabolism.

  10. Classification by Metabolism • To obtain carbon: • 1. Heterotrophs: Consume preexisting organic compounds (i.e. eating). • 2. Autotrophs: Direct uptake from the environment (self-feeding, plants)‏

  11. Classification by Metabolism • To obtain energy: • 1. Photosynthesis: sunlight • 2. chemosynthesis: chemical energy • Ingested food • Inorganic reactions

  12. 4 Metabolic Classifications • Based on energy and carbon acquisition. • 1. Photoautotrophs • 2. Chemoautotrophs • 3. Photoheterotrophs • 4. Chemoheterotrophs

  13. Liquid Water on Earth • All living cells on Earth depend on liquid water because metabolism requires: • 1. Organic chemicals are readily available for reactions. • 2. A means of transporting chemicals to and within cells; waste products away. • 3. Water plays a role in many of the reactions.

  14. DNA and Heredity • 3 key features of life on Earth • 1. structural units – cells • 2. metabolic processes – energy production • 3. owner's manual – data storage for how a cell is constructed, how it works, and how to build another one, and pass it on to the next generation - heredity.

  15. DNA Structure • Double helix • DNA bases – 4 • Adenine • Guanine • Thymine • Cytosine • Pair as AT & CG

  16. Replication • Unzip & each strand acts as a template. • Use RNA in the rebuild process.

  17. Genome • Humans have ~3 X 10^9 bases • 46 chromosomes (23 pairs)‏ • Sequences for individual instructions are called genes. • Most of DNA is “noncoding” (junk 95%)‏ • Complete sequence – genome. Some bacteria – 10^5 bases, few 10^2 genes Humans – 20,000 – 25,000 genes Rice – 37,000 genes (smaller DNA sequence)‏

  18. Genetic Code • Words consist of 3 DNA bases. • Sequence has a start and stop word. • Used to build proteins. • Redundancy (64 codes, 20 amino acids)‏ • Most amino acids are coded with the first 2 base letters only (16). Does this give a clue to evolution of complex organisms? • Nearly all living organisms have mostly similar genetic code.

  19. RNA • Uses ACG & Uracil • mRNA – transcription (carries the instr.)‏ • tRNA – transfer (gathers the AAs)‏ • rRNA – backbone of building structure. • Mutations - <1:10^9, but can have dramatic consequences. • Provide the basis for evolution. • Genetic Engineering. • RNA was probable precursor.

  20. Extreme Life - Extremophiles • Thermophiles – heat lovers • Hyperthermophiles • Black smokers (350˚C)‏ • Hot springs

  21. Extreme Life - Extremophiles • Psychrophiles – cold lovers • Antarctica ice pack (-20˚C)‏ • Also very dry Radiation hardened

  22. Extreme Life - Extremophiles • Endoliths – within rocks • Up to several km below ground • Endospores (resting) – found on moon • Could these survive interplanetary journeys?

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