Cellular Respiration

ATP Energy

ATP: Adenosine triphosphate is the main energy currency of cells.


    Why it is Ideal for Energy Usage

  • Stable at cell pH → does not break down (release energy) prematurely
  • Soluble in water → moves quickly into cell cytoplasm
  • Can’t cross membranes easily → stays where it is needed
  • Releases enough energy for most tasks within cells → little excess energy wasted (transformation to heat)
  • Can be regenerated → ADP becomes ATP easily by re-adding a 3rd phosphate

    ADP and ATP Cycle

  • ATP → ADP: 1 phosphate removed → energy released (condensation reaction)
  • ADP → ATP: 1 phosphate added→ energy needed (hydrolysis reaction)

    Processes Requiring ATP - BAM

  • 1. Biosynthesis: Anabolic reactions use ATP to synthesize macromolecules
  • 2. Active transport: ATP is required to move substances against concentration gradient
  • 3. Movement: ATP is needed to move cells or cell components (ex. chromosomes)

Respiration

Respiration: the part of metabolism in all living cells where carbon compounds are oxidized to release energy in the form of ATP. Glucose and fatty acids are common substrates, as well as amino acids.


    Cell Respiration is Different From Ventilation and Gas Exchange

  • Ventilation (breathing) is moving air in and out of lungs
  • Gas exchange is swapping one gas for another at a surface where the cell is in contact with the environment

    Aerobic Respiration vs Anaerobic:

    Oxygen used? Substrates used Combustion ATP produced per glucose Waste products Location in human cell
    Aerobic Yes Sugar/lipids Complete 30-32 (large yield) CO₂ and H₂O Cytosol + mitochondria
    Anaerobic No Glucose/other sugars Partial 2 (small yield) Lactic acid Cytosol

    Investigating the Rate of Cell Respiration

  • Respirometer: Measures O₂ uptake and CO₂ release
  • KOH (alkali) absorbs CO₂ → pressure drop = O₂ used
  • CO₂ release = drop in pH of alkali
  • Temperature must stay constant (affects air pressure)
  • Rate = O₂ used or CO₂ made, per unit time