GRE Subject Test: Biochemistry, Cell, and Molecular Biology : Help with Oxidation-Reduction Chemistry
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Example Questions
Example Question #1 : Help With Oxidation Reduction Chemistry
Consider the following reaction:
Which atom is oxidized in the reaction?
Iron
Aluminum
Oxygen
None of the atoms are oxidized
Aluminum
Oxidation is the process of losing electrons, or acquiring a more positive charge. We can determine which atom has lost electrons by comparing the oxidation number of the atom as a reactant and as a product. Aluminum is in elemental form as a reactant, so it has an oxidation number of 0. As a product, it is bonded with oxygen, giving each aluminum an oxidation number of +3. Since it has a more positive charge, the aluminum has been oxidized.
Example Question #1 : Help With Oxidation Reduction Chemistry
Which mnemonic would be most useful for remembering what happens during an oxidation-reduction reaction?
OCEAN
BARF
LEO says GER
ROME
PASS
LEO says GER
LEO says GER is a mnemonic for Loss of Electrons is Oxidation, Gain of Electrons is Reduction. An oxidation-reduction reaction is a chemical interaction in which one substance is oxidized and loses electrons, and thus is increased in positive valance, while another substance gains an equal number of electrons and is reduced, thus decreasing in positive valance. This is called a redox system or reaction. Along with LEO says GER, another popular mnemonic for this system is "OIL RIG," which stands for Oxidation is Loss, Reduction is Gain (in reference to electrons).
BARF is a mnemonic for Break (a bond) Absorb (energy), Release (energy) Form (a bond). This is used to remember whether energy is required or released when chemical bonds are broken and formed. OCEAN describes the big five personality traits: openness, conscientiousness, extraversion, agreeableness, and neuroticism. PASS stands for pull, aim, squeeze, and sweep—how to use a fire extinguisher. ROME is a mnemonic for Respiratory Opposite, Metabolic Equal. The values for the respiratory form of acid-base balance are opposite; if pH is high, carbon dioxide will be low and vice versa. For the metabolic form, the values are equal. If pH is high, carbonic acid will be high. If pH is low, carbonic acid will be low.
Example Question #1 : Chemical Reactions
Reduction of a compound results in a __________ of electrons, thus rendering the compound's charge to be more __________.
gain . . . negative
loss . . . dynamic
loss . . . negative
gain . . . positive
loss . . . positive
gain . . . negative
The process of reduction causes a gain of electrons. Because electrons are negatively charged, any compound that becomes reduced will be more negative than it was prior to the reaction.
Example Question #2 : Chemical Reactions
Which of the following is not a redox reaction?
II and III
I only
I and II
II only
III only
II only
All of the given choices represent oxidation-reduction reactions that are important in cellular metabolism. Oxidation-reduction reactions involve the changing of oxidation states (commonly through the transfer of electrons). In the first reaction NAD+ is reduced. The second reaction shows the polymerization of two molecules of glucose via a condensation (dehydration synthesis) reaction. In the third reaction glucose is oxidized.
NADH and are important electron carriers that bring electrons to the electron transport chain and are formed during glycolysis and the Krebs cycle via reduction. The final choice represents the overall oxidation-reduction reaction that occurs for one molecule of glucose.
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