C1.2 Cell Respiration ATP

ATP: The Energy Currency of the Cell

Every living organism, regardless of size or complexity, utilizes the same molecule, adenosine triphosphate (ATP), to power cellular processes.

ATP Distributes Energy Within Cells

• ATP is the primary molecule used to transfer energy within cells.
• It's an RNA nucleotide composed of:
  • A nitrogenous base: adenine
  • A 5-carbon sugar: ribose
  • A tail of three phosphate molecules
• ATP serves as the universal energy currency, facilitating various biochemical processes.
  • Transport of substances
  • Muscle contraction
  • Synthesis of large molecules

Life Processes Powered by ATP

ATP is essential for cellular processes requiring energy, including:

• Active Transport:
  • Moving molecules against their concentration gradient necessitates active transport.
  • ATP binds to transport proteins, releasing a phosphate group, which transfers energy to the protein.
  • This energy enables the protein to move the molecule across the membrane.
• Synthesis of Macromolecules (Anabolism):
  • The formation of bonds in macromolecules like proteins and DNA requires energy from ATP.
  • Enzymes catalyzing these reactions rely on ATP to function correctly.
• Movement:
  • ATP fuels cell movement and the movement of components within the cell.
  • Cell movement involves the cytoskeleton, a network of protein filaments.
  • ATP provides the energy to bond fragments together.
  • The growth and contraction of these filaments lead to changes in cell structure and movement.
  • Example: A phagocyte engulfing a bacterium uses ATP to extend its membrane around the bacterium via cytoskeleton movement.

Energy Transfers During Interconversions Between ATP and ADP

• ATP carries chemical energy within a cell.
• Hydrolysis: Breaking the bond between the second and third phosphate groups in ATP's tail releases energy in an exergonic reaction.
  • This process involves adding a water molecule (H_2O).
  • ATP is converted into adenosine diphosphate (ADP).
• Phosphorylation: The generation of ATP involves adding a phosphate group to ADP in an endergonic reaction.
  • A water molecule is removed during this process.
  • Energy is stored temporarily during ATP synthesis and released during ATP hydrolysis.