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6th Grade Science / Lesson 9 - Energy Released in a Cell

Energy Released in a Cell
What will we be learning today?


  • In this lesson, we are going to learn all about how energy is released in a cell.


How Is Energy Released in a Cell?


  • Energy for a cell's activities is locked within molecules of sugar.

  • Plants store up the sugar for their own use.

  • Animals get this energy by eating plants or other animals that have eaten plants.

  • To use the energy, cells of an organism "unlock" the energy from sugar.


  • The energy in a sugar molecule is "unlocked" or released by a process called respiration. Respiration takes place in cells in the mitochondria.

  • Think of respiration as a process of burning a fuel, such as wood or coal. Sugar is the fuel. Usually the process requires oxygen, which living things take in from air or water.

  • The sugar molecules are broken down, and energy and wastes are released. The wastes are water and carbon dioxide



  • Some cells carry on respiration without oxygen, a process called fermentation.

  • For example, oxygen may not reach all your muscle cells when you exercise. In this case fermentation releases the energy.

  • It also releases a waste called lactic acid.


  • One-celled organisms called yeasts carry on fermentation by feeding on sugars.

  • They break the sugars down and produce carbon dioxide and a kind of alcohol called ethanol.


  • Ethanol has many uses, from antifreeze to manufacturing.

  • Ethanol is also being mixed with other chemicals to produce a fuel that can power motor vehicles.

  • Scientists are working with plant products that can be fermented-wood chippings and corn, for example-to produce ethanol.


Let's Review What We Learned Today!


  • Now complete your worksheet!