6 - Biological Oxidation and Reduction Flashcards
If ΔE* (reduction potential) is more positive than ΔG* is
Negative, and vice versa. A reduction potential is positive in spontaneous reactions. Electrons flow from a species with a more negative E* to a species with a more positive E*
Living organisms use redox coenzymes for what
As high energy electron carriers (eg. NADH and FADH2)
What is the biochemical reference half reaction? What is the reduction potential of this reversible half reaction?
2H + 2e- -> H2 -0.42 V
What is the conventional direction for half reactions to be writtern in?
Each is written as a reduction.
What does reduction potential magnitude mean?
High reduction potential (eg. above 0) means greater tendency to become reduced and low reduction potential means they are better at donating electrons
Do enzymes have an effect on reaction spontaneity?
Enzymes do not affect if a reaction is spontaneous or not, they only speed it up. Only the redox potential and resulting ΔG determine the direction that is favoured and that will be spontaneous.
What direction do electrons flow in redox reactions
Electrons flow spontaneously from a species with a more negative E’ to a species with a more positive E’.
How can redox potential (ΔE) be measured?
By setting up two half reactions in seperate containers connected by a salt bridge, and voltmeter (electrochemical cell). Voltmeter is set up between the wires connecting to anode and cathode (usually made out of platinum).
ΔE° = E°(electron acceptor) - E°(electron donor)
Reactions with large negative reduction potentials have oxidized forms with the smallest tendency to accept electrons and become reduced. Therefore reduction potential E° is a measure of?
Reduction potential is measure of A REACTION (not a species). The reducing agent is always written to the right of the oxidizing agent and the number of electrons transferred.
