AP Biology - Metabolism and Enzyme

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  • 1. METABOLISM An Introduction
  • 2. ENERGY CHANGES
    • Respiration drives thousands of reactions
    • Types of energy: heat, kinetic, chemical
    • System vs. surroundings
  • 3. LAWS OF THERMODYNAMICS
    • Energy cannot be created or destroyed, only changed
    • Energy transfers increase entropy
    • “ Organisms are islands of low entropy in an increasingly random universe.”
  • 4. METABOLIC PATHWAYS
    • Regulated, multi-step flow; reactant  product
    • Uses enzymes
    • Catabolic (breaking down, releasing energy)
    • Anabolic (building, consuming energy)
  • 5. FREE ENERGY
  • 6. Δ G
    • Free energy is the portion that can perform work
    • Δ G = Δ H – T Δ S
    • Δ H: change in enthalpy
    • T: Temperature in Kelvin
    • Δ S: change in system entropy
  • 7. SPONTANEITY
    • Spontaneous processes occur without energy input (negative Δ G)
      • System must give up energy/enthalpy ( Δ H) or give up order ( Δ S)
    • Other processes need energy input (positive/zero Δ G)
  • 8. METABOLISM
    • Exergonic: releases free energy ( Δ G negative)
    • Endergonic: absorbs free energy
    • Reactions often linked/coupled
  • 9. EQUILIBRIUM
    • A closed system will reach equilibrium and do no work
    • Constant flow or energy/materials
    • maintains reactions
  • 10. ATP Energy Currency
  • 11. TYPES OF CELLULAR WORK
    • Mechanical
    • Transport
    • Chemical
  • 12. ATP STRUCTURE
    • Ribose, adenine, and 3 phosphates (negative charges)
    • Hydrolysis releases free energy
    • ATP + H 2 O  ADP + P i + energy
  • 13. ATP FUNCTION
    • Phosphorylates other molecule, which then reacts again
  • 14. ATP CYCLE
  • 15. ENZYMES
  • 16. RATES
    • Spontaneity does not imply speed
    • Enzymes = catalytic proteins
    • Enzymes lower activation energy (E A ) (often heat)
  • 17. ENZYMES AND ACTIVATION ENERGY
    • “ Heat was a bad choice”
    • No change to Δ G or reaction type
    Milk!
  • 18. ENZYMES
    • Bond to substrate, then converts it
    • End in “ –ase ”
    • Specific to one reaction due to active sites
    • 1000s per second
    • Not used up
  • 19. ENZYMES
    • Reversible
    • Catalyze towards equilibrium
    • Why do enzymes lower E A ? (pg. 153-154)
    • Rate depends on concentration
  • 20. ENZYME ACTIVITY
    • Optimal temperatures
      • In humans, 35 ° to 40 ° C
    • Optimal pH
      • In humans, 6-8
  • 21. INHIBITORS
    • Competitive inhibitors block active sites
    • Noncompetitive inhibitors attach at other locations
    • Examples: toxins like DDT, antibiotics, regulators
  • 22. ALLOSTERIC REGULATION
    • Activation/inhibition done by regulatory molecule
      • Example: ATP / ADP
  • 23. FEEDBACK INHIBITION
    • Molecules slow down their own synthesis