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Energy Molecules: ATP and ADP

By — John Wiley & Sons, Inc.
Updated on Dec 14, 2010

Cells require energy for chemical reactions such as respiration and photosynthesis. Adenosine triphosphate (ATP) is the primary energy-supplying molecule in cells. An ATP molecule is made up of three phosphate groups, each with the formula PO4. When ATP loses a phosphate group, it becomes adenosine diphosphate (ADP) and releases large amounts of energy to the cell. Eventually ADP reclaims a phosphate group and becomes high-energy ATP again. In this activity you will create a model of ATP and ADP.

Materials

Masking tape; Pen or marker; String (about two inches long); Small plastic container with lid

Activity

  1. Place the small plastic container with lid on a table.
  2. Tear off four one-inch pieces of masking tape. Write ''PO4'' on three pieces of tape. Write ''E'' on the fourth piece.
  3. Tape one PO4 on the lid of the container. Place the second PO4 near the bottom of the container (on the exterior) and the third near the middle of the container (on the exterior).
  4. Remove the lid of the container. Tape the piece of string on the underside of the lid so it dangles downward. At the free end of the string attach the E.
  5. Place the lid back on the container (with the E on the inside).The closed container represents a molecule of ATP. The E inside the container represents the energy of this molecule.
  6. Remove the lid. You have removed a PO4 and with it energy has been released. Now the molecule is called ADP. To make it ATP again, you must replace the lid.

Follow-Up Questions

  1. How many phosphates does ATP contain? What does an ATP molecule possess that is important to cell function?
  2. How many phosphates does ADP contain? What happens to it when it gains a phosphate?

Answers

  1. ATP contains three phosphates. ATP molecules are full of energy.
  2. ADP contains two phosphates. ADP gains energy.

Extension

Look up molecular diagrams of ATP and ADP. What elements are found in each of these energy molecules? What are some other energy molecules found in cells during cellular respiration?

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