Chapter 9: Energy in a Cell

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Chapter 9 Energy in a Cell

• 9-1 ATP in a Molecule
• (Source and Uses of Cell Energy)

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9-1 Energy in a Cell

• Key Concepts
• What is ATP?
• How does ATP provide energy for the cell?
• What is the role of ATP in cellular activities?
• Vocabulary
• Adenosine triphosphate (ATP)
• Adenosine di- and monophosphate (ADP, AMP)

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Cell Energy

• Energy is essential to life!!
• ? all living things must be able to
• -produce energy
• -store energy for
• future use
• -use energy in a
• controlled way.

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Which cellular activities require energy???

• Active transport
• Cell division
• Movement of flagella or cilia
• Production of proteins
• Storage of proteins

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9-1 Energy in a Cell

• Chemical Energy and ATP
• Energy can exist or be stored in many forms
• Light
• Heat
• Electricity
• Chemical Compounds (CHEMICAL BONDS!)

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9-1 Energy in a Cell

• ATP
• Adenosine TriPhosphate
• Adenine (N)
• 5-Carbon Sugar (Ribose)
• 3-phosphate groups

tri 3
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Phosphate groups

• Phosphate groups are negatively charged
  molecules
• Molecules with the same charge repel each other
  (they do not like being too close to each other)
• This means that the 3 phosphate groups on ATP are
  in a very unstable arrangement!

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Look at the bonds!!
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ATP and Energy

• This unstable arrangement of the 3 phosphate
  groups is like a compressed springstored
  potential energy!
• The third phosphate group is so eager to get away
  from the other two that, when the bond is broken,
  energy is released
• What is left over is a free phosphate group and a
  lower energy molecule ADENOSINE DIPHOSPHATE
  (ADP)

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Bonds Energy
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9-1 Energy in a Cell

• ATP
• Adenosine TriPhosphate
• Adenine (N)
• 5-Carbon Sugar (Ribose)
• 3-phosphate groups
• ADP
• Adenosine DiPhosphate
• Adenine (N)
• 5-Carbon Sugar (Ribose)
• 2-phosphate groups

tri 3
di 2
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9-1 Energy in a Cell

• Energy in ATP is released when it is converted to
  ADP (Fig. 9-2).
• The characteristics of ATP make it an
  exceptionally useful molecule that is used by all
  types of cells as their basic energy source.

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ATP / ADP Cycle

• When ATP is broken down, energy is RELEASED and
  ADP is formed.
• When ADP binds with another phosphate, energy is
  STORED and ATP is formed.

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ATP / ADP Cycle
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ATP / ADP Cycle
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9-1 Energy in a Cell

• ATP
• Efficient in transferring energy
• Not very good for storing large amounts of energy
  long term.
• A single molecule of sugar stores more than 90
  times a molecule of ATP.

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How do cells use the energy stored in ATP?

• Cellular proteins have a
• specific site where ATP
• can bind
• When the ATP breaks down,
• the energy is transferred to
• the protein, enabling the protein
• to DO WORK
• (e.g. active transport, move, change shape)

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Battery analogy

• Sitting on a table, batteries are not of much
  use
• Put the batteries into a device (radio, cell
  phone, etc.) and the stored energy in the battery
  is put to use!
• When the battery is dead it can be removed and
  recharged

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Bonds Energy
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Battery analogy

• The energy stored in ATP is available when ATP is
  bound to a protein that will use it
• Once the ATP is dead (is not ADP), it is
  released to be recharged back into ATP.

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