Students learn about the basics of cellular respiration. They also learn about the application of cellular respiration to engineering and bioremediation. And, they are introduced to the process of bioremediation and examples of how bioremediation is used during the cleanup of environmental contaminants.

In bioremediation, bacteria digest toxic compounds and break them down into harmless byproducts in a process that is analogous to the way humans eat, breathe and produce waste. Engineers can monitor whether bioremediation is occurring by measuring a decrease in what the bacteria are "inhaling" and an increase in what they are "exhaling." Measuring these results of cell functions is a generally easier process than trying to keep track of the actual amount of toxic material that exists. In bioremediation, engineers promote the growth of cells that break down toxic compounds into harmless byproducts. By understanding how the cells "breathe," engineers can monitor cell growth by measuring the changes in concentration of chemicals that bacteria "inhale" and "exhale." bioremediation cells cellular respiration electron transport chain food energy glycolysis krebs cycle photosynthesis After this lesson, students should be able to: Explain the purpose of cellular respiration. Describe bioremediation. Give examples of when engineers use bioremediation to clean up the environment. Did you know that all cells, even plant cells, grow and reproduce through cellular respiration? Cells get energy from their food by breaking it into water and carbon dioxide. Cells require oxygen to breathe and carbon-based food sources from the environment to get energy. Here is a simplified chemical reaction that is used to describe cellular respiration (write it on the board): This equation tells us that cells need food and oxygen in order to get energy from their environment. The energy that the food and oxygen help produce is used for the cell to grow, live and reproduce. Cells can actually use many different types of food in this equation; the food just needs to be carbon based. The three main steps in cellular respiration are: glycolysis, the Krebs cycle, and the electron transport chain. The main purpose of all these complex steps is to get energy for the organism to grow, survive and reproduce. The steps of cellular respiration take place in the cytoplasm of prokaryotic cells and the cytoplasm and mitochondria of eukaryotic cells. Engineers have developed a way to use cells that like to eat pollution (as their food source) to clean up the environment. These cells can help clean up polluted soil and water by eating the contaminants. Has anyone heard the work bioremediation before? Bioremediation is when something living, like a microorganism, fungi or green plant, is used to return a polluted environment back to an unpolluted, original state. Bioremediation is a process used by environmental engineers to clean up polluted areas. Some examples of pollutants that bioremediation can be used to clean up are oil, fuel and cleaning agents. Bioremediation can be classified two ways: in situ, when something is introduced to the contaminated area, or ex situ, when the contaminated area is removed and bioremediation is done elsewhere. Microorganisms are often used for bioremediation of oils and detergents. Microorganisms cannot be used for some things, including heavy metals. In the case of contamination by metals such as lead and mercury, plants are used for bioremediation because they can store the heavy metals in the parts of the plant that are above ground and can be harvested for removal. The three steps to cellular respiration are: glycolysis, the krebs cycle (also called the citric acid cycle), and the electron transport chain. In glycolysis, the cell turns the carbon-based food source into ATP (adenosine 5 triphosphate) for energy and other byproducts. This part of the cycle does not require oxygen and is also part of anaerobic cellular metabolism. The byproducts of glycolysis are converted to more ATP in the Krebs cycle. The Krebs cycle takes place in the mitochondria of the cell. Enzymes are used to break down the food further and produce ATP. In the final part of cellular respiration, the electron transport chain, the cell uses oxygen to replenish the molecules needed to keep the Krebs cycle going. The cell gets rid of extra electrons produced in the Krebs cycle. O2 is converted to CO2. All parts of cellular respiration use enzymes. Enzymes are proteins made by the cell that help the cell break bonds in the food molecules to make energy for cellular growth and reproduction. The process where cells convert food into energy for metabolic processes. The third step in cellular respiration; the process whereby cells convert energy into ATP that can then be used by the cells to run metabolic processes. The first step in cellular respiration whereby carbon molecules (food) is converted into energy by the cell. The second step in cellular respiration whereby carbon molecules are converted into ATP, water and CO2. Plants form carbohydrate molecules that the cell can later use as an energy source from CO2, sunlight and water. Breathing Cells Who can tell me what cells require for life, or to complete cellular respiration? (Answer: they need water, oxygen and a carbon-based food source.) So, we learned today that cells break down "food" during cellular respiration to get energy for growth, survival and reproduction. Engineers use their understanding of cells and cellular respiration to clean up contamination in the environment through a process called bioremediation. Bioremediation involves microorganisms, fungi and plants whose cells can "eat" pollution for food in order to remove that pollution from soil and water. These cells convert contaminants into energy through cellular respiration which they then use to sustain their life. Discussion Question: Ask a discussion question to get students to think about the upcoming lesson. After soliciting answers, explain that these questions will be answered during the lesson. What does a cell need to grow, survive and reproduce? Question/Answer: Ask the students questions and have them raise their hands to respond. Write their answers on the board. What is cellular respiration? (Answer: The process in which cells convert food into energy for growth and reproduction.) What type of food source does a cell need for cellular respiration? (Answer: A carbon-based food source.) How do engineers use cellular respiration to clean up the environment? (Answer: Engineers use cellular respiration through bioremediation to clean up the environment. Bioremediation is a process in which cells are used to remove toxins from soil and water.) What do the cells do with the pollutants during bioremediation? (Answer: The cells digest the pollutants and convert the carbon-based source into energy for growth and reproduction. The cells help remove the pollutants from the environment.) Engineering Bioremediation Impacts: Have the students think about the impacts of engineering bioremediation on individuals, society and the environment. As a class, list the pros and cons of bioremediation in cleaning up a contaminated environment. Have students research different types of bioremediation that are in use today. Some examples include bioventing, phytoremediation, bioreactors, composting, biostimulation and rhizofiltration. Have students learn more about using plants for bioremediation. Which plants are most successful in bioremediation? Some examples include sunflowers, ragweed, poplar trees, and sugar beets. What types of environmental contaminants have been removed successfully using plants? This lesson can be combined with the lesson about photosynthesis since they are opposites. Cellular respiration consumes the products of photosynthesis and vice versa. It is important to mention that plants perform both cellular respiration and photosynthesis while animals only perform cellular respiration. National Cancer Institute, Surveillance, Epidemiology and End Results (SEER) Program, September 2000, accessed September 26, 2008, <http://training.seer.cancer.gov/module_anatomy/images/illu_cell_structure.jpg>