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Investigation 5.4
ADP-ATP Cycle |
Before we look at ATP, lets think about some of the by-products of cellular respiration, water and carbon dioxide. As you may know we often see water represented as H2O. Water is made of hydrogen and oxygen. Carbon dioxide (CO2) is made of carbon and oxygen. These are both by-products of glucose, which is made of carbon, hydrogen, and oxygen," burning " in the mitochondria. Glucose is made up of 6 carbon atoms, twelve hydrogen atoms, and 6 oxygen atoms. |
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If we say that nothing is ever lost, what must be happening to the glucose when it is" burned " in the mitochondria? |
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Do we still have glucose at the end? |
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Talk to your group and see if you can come up with a model of what happens in this chemical reaction that allows water and carbon dioxide to be made from what is left when glucose" burns " . |
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Next talk to your group and see if you can come up with an idea about what happens to the oxygen, carbon dioxide, and hydrogen. |
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Remember that the incoming products are just changed from one form into another. In the process energy is given off. We will talk about what this energy is used for in the next lesson. |
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Share your group ideas with the rest of the class. Can you support your answer? Can others? |
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Ask them some questions you have about their model. |
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Do some of these new ideas sound possible? |
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Now let's look specifically at the ATP that is produced. Think back to the fire analogy and the discussion you just had on chemical change. |
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Heat is released when the fire burns. Some heat is also released in the mitochondria. |
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What do you think happens inside of the mitochondria with this energy, is it freely released or is captured? |
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What evidence do you have to support your idea? Draw your ideas. |
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Discuss this with your group and see if you can come up with a group model for what happens when glucose is used to make ATP. |
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The cell is more efficient than a simple fire in that it grabs the energy released by the glucose and stores it in high energy molecules called ATP. |
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Already inside the mitochondria are molecules called ADP. |
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These are low energy molecules, too weak to provide the energy needs of the cell. |
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When the glucose is burned, it releases energy to glue a free phosphate (P) onto the weak ADP molecule. |
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Compare this model to the model your group came up with. Are there any similarities? |
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| Breaking the Phosphate Bond |
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Sometimes it is difficult to understand how tiny molecules like ATP that we cannot see can release energy to do all the things our bodies do all day and night. |
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