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Aerobic Respiration

The controlled use of fire marks a pivotal technological advancement that distinguishes Homo from other animals. Approximately 1.5 million years ago, archaeological sites in Asia and Europe reveal that this innovation coincided with Homo erectus remains. Fire represents a crucial source of energy, enabling early humans to cook food, heat shelters, and enhance survival in diverse climates. Understanding the chemical processes of combustion reveals how oxidation, a common thread in cellular respiration and fire, fundamentally supports life. This mastery of fire facilitated humans' expansion across the planet.

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Aerobic Respiration

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Presentation Transcript

  1. Do Now: Aerobic Respiration

  2. Early Human Technology • What earliest technology makes homo unique among animals? Pan troglodyte Homo neanderthalis Ardipithicus(4.4 MYA)

  3. Not Tools… Chimpanzees use those too

  4. FIRE!!! • Archaeological sites in Asia and Europe indicate the first controlled use of fire occurred about 1,500,000 years ago. • The location of these ancient campfires coincides with the discovery of Homo erectus remains.

  5. The Importance of Fire • Chemically speaking, fire is a product of the oxidation of biomass. It is a very exothermic process. • CH2O + O2 CO2 + H2O • Fire releases the energy stored by plants during photosynthesis

  6. Fire & Cellular Respiration – Same Thing!!! • The examples shown have different amounts of energy stored in them. Rank them from least energy to greatest

  7. What Fire Represents • The discovery of fire represented an increase in the amount of energy available to humans. • We have used this energy to increase our numbers and colonize every continent! • Fire, and the combustion of fossil fuels, is nothing but an extension of our metabolic processes by other means.

  8. Burning = “Oxidation” • Oxidation state measures changes in the electronic structure of an atom • In general, a lower oxidation number represents a higher energy state. • Take carbon, for example: • CO2 = +4 ; C = 0 ; CH4 = -4

  9. Oxidation State of Carbon in: Lipids and Protein < -1 Carbohydrates 0 Hydrocarbons < -2 More Energy Less Oxidized Less Energy More Oxidized

  10. Oxidation and Reduction • Whenever something gets oxidized, the thing that oxidizes it gets reduced. • 2Fe +3O2 2Fe2O3 • Before the reaction, Fe = 0, O = 0 • After, Fe = +3, O = -2 • For every yin, there is a yang.

  11. What Does All This Mean??? • As usual, it’s all about the electrons.

  12. So… The bottom line • When a substance is oxidized, it: • Releases energy (exothermic) • Looses electrons • Increases oxidation state • Carbon is oxidized when burned, or used in cellular respiration. • Carbon is reduced during photosynthesis.

  13. Example: Burn Sugar and Follow the Carbon • C6H12O6 + 6O2 6CO2 + 6H2O • Before the exothermic reaction, the carbon in C6H12O6 has an oxidation number of 0. • During the reaction, carbon looses electrons. • After the reaction, the carbon (now in CO2) has an oxidation number of +4. • Carbon has been oxidized.

  14. Carbon Oxidation = Aerobic Life • The oxidation of carbon is the biochemical basis upon which almost all life rests. • The rate at which an individual or population can survive, grow, and reproduce is limited by how quickly it can get energy by oxidizing carbon.

  15. The Fire Outside… • Fire greatly increased homo’s access to energy. • With it, humans and their ancestors could: • Cook food, making new sources of nutrition available • Heat shelters, allowing them to live in colder climates • Carry a portable source of light.

  16. Growth requires Carbon

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