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AEROBIC RESPIRATION
Do Now:
Early Human Technology
What earliest technology makes homo unique among animals?
Homo neanderthalis Ardipithicus (4.4 MYA)
Pan troglodyte
Not Tools… Chimpanzees use those too
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.
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
Fire & Cellular Respiration – Same Thing!!!
The examples shown have different amounts of energy stored in them. Rank them from least energy to greatest
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.
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
Oxidation State of Carbon in:
Carbohydrates 0
Lipids and Protein< -1 Hydrocarbons
< -2
Less EnergyMore Oxidized
More EnergyLess Oxidized
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.
What Does All This Mean???
As usual, it’s all about the electrons.
So… The bottom line
When a substance is oxidized, it:Releases energy (exothermic)Looses electronsIncreases oxidation state
Carbon is oxidized when burned, or used in cellular respiration.
Carbon is reduced during photosynthesis.
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.
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.
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.
Growth requires Carbon
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