AP Biology Unit 3 Review

• What are the key properties of enzymes?


  Enzymes are usually proteins that lower activation energy and are highly specific
• How do enzymes affect the activation energy of reactions?


  They lower the activation energy, increasing the reaction rate
• Describe the structure and function of enzymes.


  • Enzymes are usually proteins
  • Some RNAs act as enzymes
  • They catalyze reactions by lowering activation energy
  • Highly specific due to active site shape and charge
• What is the role of the active site in an enzyme?


  The active site complements the shape and charge of the substrate
• How does pH affect enzyme activity?


  Most enzymes have a pH optimum where they operate at peak efficiency
• What happens to enzymes when the pH changes significantly from their optimum?


  Enzyme performance drops due to denaturation
• How does temperature affect enzyme activity?


  Enzyme activity increases with temperature up to a certain point
• What occurs to an enzyme at high temperatures?


  The enzyme denatures, reducing its catalytic ability
• Compare reversible and irreversible enzyme denaturation.


  • Reversible denaturation: enzyme function can be restored by optimal conditions
  • Irreversible denaturation: enzyme shape is permanently changed, function destroyed
• How does substrate concentration affect enzyme activity?


  Low substrate concentrations result in low reaction rates, while higher concentrations increase the rate until saturation
• What is competitive inhibition in enzymes?


  • A foreign molecule blocks the enzyme's active site
  • Prevents substrate from binding
  • Inhibits the rate of the reaction
• What is non-competitive inhibition in enzymes?


  • A foreign molecule binds to the allosteric site
  • Changes the shape of the active site
  • Prevents substrate from binding
• What is a metabolic pathway?


  • A linked series of enzyme-catalyzed reactions
  • Involves reactants, intermediates, and products
  • Examples include glycolysis, Krebs cycle, and Calvin cycle
• What are autotrophs?


  Organisms that can produce their own food
• What is the difference between photoautotrophs and chemoautotrophs?


  Photoautotrophs use light energy, while chemoautotrophs oxidize inorganic substances for energy
• What are heterotrophs?


  Organisms that capture energy from organic compounds produced by other organisms
• What is the difference between exergonic and endergonic reactions?


  Exergonic reactions release energy, while endergonic reactions require energy
• What is the structure of ATP?


  ATP consists of a ribose sugar, adenine base, and three phosphate groups
• How is ATP used to store and release energy?


  Cells combine ADP and a phosphate group to form ATP for storage and release energy by breaking off a phosphate group
• What is energy coupling?


  Energy coupling links an exergonic reaction to drive an endergonic reaction forward
• What is the chemical equation for photosynthesis?


  6 CO₂ + 6 H₂O + light energy → C₆H₁₂O₆ + 6 O₂
• What type of reaction is photosynthesis?


  Photosynthesis is an endergonic reaction
• What are the two phases of photosynthesis?


  1. Light reactions: convert light energy into ATP and NADPH
  2. Calvin cycle: converts ATP and NADPH into carbohydrates using CO₂
• What is the role of chlorophyll in photosynthesis?


  Chlorophyll absorbs light energy to help convert it into electrical energy
• What does the absorption spectrum of chlorophyll show?


  It shows the amount of light absorbed at different wavelengths
• Why are leaves green?


  Leaves reflect green light while absorbing other wavelengths
• What is the action spectrum of photosynthesis?


  The action spectrum shows how various light wavelengths drive photosynthesis
• Who conducted the experiment that determined the action spectrum of photosynthesis?

  Thomas Engelman
• What did Engelman's experiment demonstrate?


  It showed that blue and red light drive the most photosynthesis
• What colors of light do chlorophyll absorb the most?


  Blue and red
• Why do leaves appear green?


  Because they reflect green light while absorbing other wavelengths
• What is a carotenoid?


  A pigment that absorbs other wavelengths of light in photosynthesis
• What does the action spectrum of photosynthesis show?


  How various light wavelengths drive photosynthesis
• Who conducted the Engelman experiment?


  Thomas Engelman
• What did Engelman's experiment demonstrate about light wavelengths?


  Aerobic bacteria grew best in blue and red light, indicating higher oxygen production
• What is the spinach leaf disc experiment used to demonstrate?


  • The rate of photosynthesis
  • Discs rise based on oxygen production
  • Variables include light intensity and wavelength
• Where are chloroplasts found?


  In the cells of the leaf
• What are the main components of a chloroplast?


  Outer membrane, inner membrane, DNA, ribosomes, thylakoids, and stroma
• What is the function of thylakoids in chloroplasts?


  They contain the membrane-bound photosystems and chlorophyll for light reactions
• What is the stroma in chloroplasts?


  The fluid surrounding thylakoids where the Calvin cycle occurs