AP Bio

• Gibbs free energy


  The energy available to do work
• Gibbs free energy equation

  Delta G = Delta H - T * Delta S
• Endergonic reaction


  Reaction that absorbs energy (positive Delta G)
• Exergonic reaction


  Reaction that releases energy (negative Delta G)
• Enzyme


  Biological catalyst that speeds up chemical reactions by lowering activation energy
• Enzymes


  • They are proteins
  • They are not consumed by the reaction
  • They only affect activation energy, not Delta G
• How enzymes work


  1. Substrate binds to active site

  2. Enzyme changes shape (induced fit)

  3. Reaction occurs

  4. Products are released
• Competitive inhibitor


  Binds to the same active site as the substrate, competing for binding
• Non-competitive inhibitor


  Binds to an allosteric site, changing the shape of the active site
• Reversible inhibitor


  Inhibitor can unbind, allowing substrate to bind again
• Irreversible inhibitor


  Inhibitor binds permanently, preventing substrate from binding
• Denaturation


  Unraveling of a protein's secondary, tertiary or quaternary structure
• Factors that cause denaturation

  • High temperature
  • Extreme pH
  • High salinity
• pH


  Too low or too high pH will cause denaturation of proteins
• Factors that affect enzymes

  • Temperature
  • pH
• pH affecting enzymes


  • Milk going sour due to bacteria producing lactic acid, decreasing pH
• Salinity


  Positive and negative charges in salt can mess with the polarity of proteins, causing denaturation
• Allosteric inhibition


  Considered the same as non-competitive inhibition, as allosteric means binding to another location
• Cellular respiration


  1. Glycolysis

  2. Krebs cycle

  3. Oxidative phosphorylation
• Glycolysis


  Takes place in the cytosol, produces 2 ATP, 2 NADH, and 2 pyruvate
• NADH


  Holds the high-energy electrons released during oxidation of glucose
• Pyruvate oxidation


  Pyruvate is converted to acetyl-CoA, releasing 1 CO2 and 1 NADH
• Krebs cycle


  Acetyl-CoA enters, 1 CO2 is released per turn, produces 3 NADH, 1 FADH2, and 1 ATP
• Krebs cycle


  • Takes place in the mitochondrial matrix
  • Requires oxygen
• Oxidative phosphorylation


  1. Electron transport chain

  2. Chemiosmosis
• Electron transport chain


  Electrons are passed down the chain, releasing energy used to pump protons across the membrane
• Chemiosmosis


  Protons flow back through ATP synthase, providing energy to phosphorylate ADP to ATP
• Oxidative phosphorylation produces heat
• There is a type of respiration in brown fat cells that generates heat without producing ATP
• Outer membrane


  The outer part of the membrane system
• Inner membrane


  The highly folded inner part of the membrane system where the electron transport chain is located
• The electron transport chain is located in the inner membrane
• Glycolysis, the Krebs cycle, and the electron transport chain are not needed to be known in detail for the exam
• What is important to know about ATP synthesis


  What goes in, what comes out, why it is important
• ATP synthesis


  1. Glycolysis makes NADH

  2. Electron transport chain

  3. Substrate level phosphorylation makes NADH and GTP

  4. Proton gradient allows ATP synthase to synthesize ATP
• The inner membrane is also called the cristae
• Steps of photosynthesis


  • Light reactions
  • Calvin cycle
• Thylakoid membrane


  Where the light reactions of photosynthesis take place
• Photosystem 1 and 2

  Photosystems that absorb light energy and transfer electrons in the light reactions
• Light reactions


  1. Light energy excites electrons in chlorophyll

  2. Electrons are transferred down an electron transport chain

  3. Proton gradient is formed

  4. ATP and NADPH are produced