ADP — Science definition

Adenosine diphosphate; it can be converted to ATP using an energy source and phosphate.

Where it is taught

In use

It is regenerated from ADP and phosphate rather than functioning as a one-time stock consumed forever.

ATP & the Flow of Energy

Questions using adp

Problem 1

What is the main difference between ATP and ADP?
  1. ATP contains DNA while ADP does not
  2. They are identical molecules with different names
  3. ATP has three phosphate groups and ADP has two
  4. ATP has two phosphate groups and ADP has three
Answer and explanation

ATP has three phosphate groups and ADP has two

ATP has three phosphate groups; ADP has two. Hydrolysis forms ADP and inorganic phosphate.

Problem 2

Describe the ATP–ADP cycle and explain why ATP is called a currency rather than a store of energy.
Answer and explanation

ATP is hydrolysed to ADP and inorganic phosphate, releasing energy that is coupled to cellular work, and ADP is then recombined with phosphate using energy released by the breakdown of fuels. The cycle runs continuously. ATP is a currency because cells hold only a few seconds' worth and regenerate it as fast as they spend it; the long-term store is in fuel molecules such as glycogen and fat, which are converted into ATP as needed.

Response criteria

  • State a biologically accurate conclusion.
  • Show the data, mechanism, or calculation that supports it.
  • Include units, conditions, or limits where relevant.

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