REDOX Reactions explained

In a redox reaction,

• the electron donor is the substance oxidized

• the electron acceptor is the substance reduced

• Oxidation is the loss of electrons

• Reduction is the gain of electrons

• OIL RIG

These reactions are important in biology because redox reactions release energy to form ATP

In cells,

• NAD⁺ /NADH is an electron plus proton carrier

  • Transports 2 electrons and 1 hydrogen at the same time

  • NADH is a good electron donor

  • NAD⁺ is a weak electron acceptor

  • Coenzymes such as these enhance diversity of redox reactions possible in a cell by allowing chemically dissimilar electron donors and acceptors to interact

Redox towers rank common half-reactions by their standard reduction potential (E₀’)

• Reduction potentia (E₀’), in volts, describes the "ability" of a compound to gain electrons (and be reduced)

• Redox towers have the most negative E₀’ at the top

  • Reduced substances

  • Most likely to be electron donators

• The most positive E₀’ are at the bottom of the tower

  • oxidized substances

  • Most likely to be electron acceptors

  • O₂ is the strongest electron acceptor

• Difference in reduction potentials between donor and acceptor is ΔE₀’

  • Greater the difference = more energy released

  • ΔE₀’ < 0 means the reaction is unfavorable (consumes energy)

  • ΔE₀’ > 0 means the reaction is favorable (releases energy)

  • ΔE₀’ is proportional to ΔG