CHAPTER 5 Summary

• All living organisms require energy to live and grow. The ultimate source of energy on Earth is the sun.
• Photosynthesis is a series of chemical reactions that captures the energy of sunlight and converts it into chemical energy in the form of sugar and other energy-rich molecules. This energy is used by all living organisms to fuel cellular processes.
• Photosynthesis can be divided into two main parts: a “photo” part, during which the pigment chlorophyll captures light energy, and a “synthesis” part, during which captured energy is used to fix carbon dioxide into glucose.
• Photosynthetic organisms are known as autotrophs; they include plants, algae, and some bacteria. Animals do not photosynthesize; they are known as heterotrophs.
• Energy is neither created nor destroyed, but is converted from one form into another, a principle known as the conservation of energy.
• Kinetic energy is the energy of motion and includes heat energy and light energy. Potential energy is stored energy and includes chemical energy.
• Energy flows from the sun, is captured and transferred through living organisms, and then flows back into the environment as heat.
• Energy conversions are inefficient. Some energy is lost as heat with every conversion of energy.
• The energy-rich molecules produced by some photosynthetic algae include oils that can be used as fuel to power automobiles and aircraft. These biofuels show great promise as alternatives to fossil fuels.

• MORE TO EXPLORE

  • U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, Biomass Program http://www1.eere.energy.gov/biomass/
  • Sheehan, J., et al. (1998) A look back at the U.S. Department of Energy’s Aquatic Species Program: biodiesel from algae. National Renewable Energy Laboratory NREL/TP-580-24190.
  • Hunter-Cevera, J., et al. (2012) Sustainable development of algal biofuels. National Academy of Sciences Report.
  • Pienkos, P. T., and Darzins, A. (2009) The promise and challenges of microalgal-derived biofuels. Biofuels, Bioproducts and Biorefining 3:431–440.
  • Groom, M. J., et al. (2008) Biofuels and biodiversity: principles for creating better policies for biofuel production. Conservation Biology 22:602–609.
  • Biello, D. (2011) The false promise of biofuels. Scientific American 302:58–65.