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Page history last edited by gerryc 15 years ago

O5. Energy is required to maintain life.


Student Outcome: O5.1

Understand that energy is required for growth, movement, repair, and reproduction.



Life is an energy intensive process. It takes energy to operate muscles, extract wastes, make new cells, heal wounds, even to think. It’s in an organism’s cells where all this energy is spent. In some cells, as much as half of a cell’s energy output is used to transfer molecules across the cell membrane, a process called ‘active transport.’


Cell movements require energy and thousands of energy-hungry chemical reactions go on in every living cell, every second, every day. The kind of energy cells use is chemical bond energy, the shared electrons that holds atoms together in molecules.


Source: http://ebiomedia.com/prod/LC/LCenergy.html


All of metabolism can be categorized as either anabolic or catabolic. In cells:

  • anabolism
    • is the synthesis of molecules, a building process that requires energy input resulting in a more highly ordered chemical organization and the increase of free energy of the products. Entropy decreases (order increases). A major downhill avenue of catabolism is cellular respiration. Glucose is oxidized to water, CO2 and energy (see ATP).
  • catabolism
    • These opposing metabolic pathways are frequently coupled so that energy released by "downhill" exergonic reactions can be used to fuel the "uphill" endergonic ones. Coupling often involves ionic gradients.
    • produces the breakdown of complex molecules to simpler ones, releasing energy which results in the decrease of chemical organization as well as the supply of free energy. Entropy increases (order decreases)



Enzymes direct traffic by selectively accelerating those steps which are most necessary to the cell at any given time during its life cycle. Homeostatic mechanisms that regulate enzymes balance metabolic supply and demand - resulting in the most energy efficient system possible.


Source: http://home.earthlink.net/~dayvdanls/CellEnergy1.html




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