Exam 4 Review:  Chapter 24:  Oxidation Reduction Reactions

anaerobic - (1) a process not depending on free oxygen or air, e.g., anaerobic glycolysis; (2)  living or occurring only in the absence of oxygen, e.g., anaerobic bacteria. 

aerobic - (1) a process depending on free oxygen or air, e.g., aerobic glycolysis; (2) involving or improving oxygen consumption by the body, e.g., aerobic exercise; (3) living or occurring only in the presence of oxygen, e.g., aerobic bacteria.

oxidation - Any chemical reaction in which the atoms in an element lose electrons and the valence of the element is correspondingly increased; the products of such reactions tend to have less potential chemical energy; often, but not always, the loss of electrons is caused by the addition of an oxygen atom to the molecule; they always occur coupled to reduction reactions.

reduction - Any chemical reaction in which one or more hydrogens is combined with a compound or in which one or more oxygens is removed from a compound; is  such reactions, there is a decrease in the positive valence or an increase in negative valence by the gaining of electrons; the products of such reactions tend to have more potential chemical energy; they always occur coupled to oxidation reactions.

oxidation reduction reactions - Any pair of coupled chemical reactions, one an oxidation and the other a reduction, in which one or more electrons are transferred from one atom or molecule to another atom or molecule, changing the oxidation number (valence) of both; the electron donor becomes oxidized and its oxidation number (valence) increases; the electron acceptor becomes reduced and its oxidation number (valence) decreases; energy is transferred in the process from the oxidized compound, the electron donor, to the reduced compound, the electon acceptor.  Nickname - redox reactions.

dehydrogenation reactions - A diverse group of biological oxidation reactions in which one or more hydrogen ions or protons are removed from a molecule along with the removal of useful chemical energy in the form of energetic electrons which will be transferred to some other molecule(s) in a coupled reduction reaction; these reactions are usually catalyzed by dehydrogenase enzymes; in living organisms, cellular respiration is actually a process of oxidation of nutrients wherein some steps involve dehydrogenation.

electron carriers - A diverse group of intermediary compounds, often coenzymes derived by modification from certain ingested water-soluble vitamins, and often joined to nucleotide containing a nitrogenous base, e.g., adenine, which participate reversibly in oxidation reduction reactions and take part by transferring energetic electrons removed from some oxidized substrate and delivering them to another molecule which will become a reduced product of the coupled reaction; e.g., Nicotinamide Adenine Dinucleotide (NAD), Nicotinamide Adenine Dinucleotide Phosphate (NADP), Flavin Mono-Nucleotide (FMN), and the Flavin Adenine Dinucleotide (FAD) and the quinones, e.g., Coenzyme Q, found within the lipid membrane in mitochondria.

coenzymes - Any of the  non-protein organic substances which usually contains a vitamin or mineral and are frequently phosphorylated, which combine with a specific protein, the apoenzyme, to form an active enzyme system by activating the apoenzyme protein, e.g., Adenosine Triphosphate (ATP), Coenzyme A, and many of the electron carriers, e.g., Nicotinamide Adenine Dinucleotide (NAD), Nicotinamide Adenine Dinucleotide Phosphate (NADP), Flavin Mono-Nucleotide (FMN), and the Flavin Adenine Dinucleotide (FAD).

Nicotinamide Adenine Dinucleotide (NAD) - A coenzyme, C₂₁H₂₇N₇O₁₄P₂, derived from the B vitamin nicotinic acid; an electon carrier and hydrogen carrier occurring in most living cells, and utilized alternately with NADH as an oxidizing or reducing agent in various metabolic processes, e.g., in various steps in the oxidation of glucose.

Flavin Adenine Dinucleotide (FAD) - A coenzyme, C₂₇H₃₃N₉O₁₅P₂, derived from the B vitamin riboflavin; an electon carrier and hydrogen carrier occurring in most living cells, and utilized alternately with FADH as an oxidizing or reducing agent in various metabolic processes, e.g., in certain step in the oxidation of glucose within the citric acid cycle.

electron transport chain - A series of membrane-bound electron carriers, various quinones, iron-sulfur (FeS) proteins, and cytochromes, located in the inner cristae membrane of mitochondria which receive energetic electrons from various electron carriers, and various related membrane-bound dehydrogenase enzymes, which use that energy in a stepwise series of oxidation reduction reactions to create a proton motive force (chemiosmosis) which pumps hydrogen ions from the matrix of the mitochondria to the intermembrane space which will ultimately be used by ATP Synthetase to generate ATPs.  aka - electron transport system, cytochrome chain, cytochrome system.

          (1)  C₆H₁₂O₆ + 6O₂ Û 6CO₂ + 6H₂O + 36 ATP + waste heat

          (2)  NAD⁺ + 2e^- + 2H⁺ Û NADH⁺ + H⁺

          (3)  pyruvate + NADH⁺ + H⁺ Û lactate + NAD⁺   

                [Note:  There are many other specific examples in metabolism, including many in fundamental glucose metabolism.] 

Sketch and Label:

2. a simplified diagram of the four stages of glucose catabolism.  Account for the CO₂, electrons (= hydrogens), and ATP extracted or produced in each stage, accounting for the energy yield from one glucose.

(1)  Glycolysis:  no CO2, net gain two ATPs, 2 electron pairs (NADH+ + H+) (2)  Formation of Acetyl Coenzyme A:  two CO2, no ATP, 2 electron pairs (NADH+ + H+) (3)  Kreb's Cycle:  four CO2, two ATPs, 6 electron pairs (NADH+ + H+) and 2 electron pairs (FADH+ + H+) (4)  Electron Transport Chain:  no CO2, 32 or 34 ATPs, no electron pairs