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Questions and Answers
What is the estimated efficiency of glucose oxidation assuming 38 ATP formed?
What is the actual ΔG value for ATP hydrolysis under cellular conditions?
What is the role of Rotenone in the Electron Transport Chain?
Which of the following is a transport inhibitor that prevents the export of ATP?
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What is the effect of Atractyloside on Complex V?
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What is the role of 2,4-Dinitrophenol (DNP) in the Electron Transport Chain?
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What is the effect of Oligomycin on the Electron Transport Chain?
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What is the byproduct of the Electron Transport Chain?
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What is the effect of Malonate on the Electron Transport Chain?
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What is the estimated efficiency of energy recovery in cells?
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Study Notes
Bioenergetics and Thermodynamics
The Variation of Equilibrium Constant with ΔGo'
- The equilibrium constant (Keq) varies with ΔGo' (Gibbs free energy)
- A higher Keq value indicates a forward reaction, while a lower Keq value indicates a reverse reaction
- When ΔGo' is negative, the reaction proceeds forward (spontaneous)
- When ΔGo' is positive, the reaction proceeds in reverse (non-spontaneous)
- At equilibrium, ΔGo' is zero
Hydrolysis of ATP
- Adenosine Triphosphate (ATP) is the primary energy currency of the cell
- ATP has an adenosine backbone with three phosphate groups (α, β, and γ)
- The hydrolysis of ATP releases energy, which is used to drive cellular reactions
Energy of ATP Hydrolysis
- The free energy of ATP hydrolysis can be calculated using the equation: ΔG = ΔG° + RT ln([ATP]/[ADP][Pi])
- In a living cell, the concentrations of ATP, ADP, and Pi are 10mM, 1mM, and 10mM, respectively
- The calculated ΔG value for ATP hydrolysis is -30.5 kJ/mol
Coupled Reactions
- Coupled reactions involve two or more reactions that occur simultaneously
- The first reaction is exergonic, releasing energy, which is then used to drive the second reaction
- The second reaction is endergonic, requiring energy to proceed
- ATP is often involved in coupled reactions, providing the energy needed to drive the reaction forward
Example of a Coupled Reaction
- Hydrolysis of creatine phosphate releases energy, which is used to form ATP
- The coupled reaction is: Creatine-PO4 + H2O → Creatine + HPO4-3 + energy, and ADP + HPO4-3 + energy → ATP + H2O
DG0 is Additive
- The free energy change (ΔG0) is additive for a series of reactions
- The total ΔG0 value can be calculated by summing the ΔG0 values of each individual reaction
ATP is Coupled to Glucose Phosphorylation
- ATP hydrolysis is coupled to glucose phosphorylation, allowing the energy from ATP to drive the reaction forward
- The reaction is: Glucose + ATP → Glucose-6-phosphate + ADP, with a ΔG0 value of -16.2 kJ/mol
Exergonic and Endergonic Reactions
- Exergonic reactions release energy, while endergonic reactions require energy to proceed
- Bonds are formed or broken during chemical reactions, resulting in the release or absorption of energy
- Redox reactions involve the transfer of electrons, resulting in a change in energy
Redox Potential
- The redox potential is a measure of the tendency of a substance to lose or gain electrons
- A higher redox potential indicates a greater tendency to lose electrons, while a lower redox potential indicates a greater tendency to gain electrons
- The difference in redox potential (ΔE) between two substances drives the flow of electrons from one substance to another
Half Reactions
- Half reactions are individual reactions that combine to form a whole reaction
- Each half reaction involves the loss or gain of electrons
- The voltage (E) of a half reaction can be calculated using the equation: E = E°' - RT/nF (ln [reduced]/[oxidized])
Cell and Half Cell
- A cell consists of two half cells, each with its own half reaction
- The voltage of the cell can be calculated by summing the voltages of the two half cells
Inhibitors of Electron Transport
- Inhibitors of electron transport can block the flow of electrons, reducing ATP production
- Examples of inhibitors include rotenone, antimycin, cyanide, and malonate
- Uncoupling agents, such as 2,4-dinitrophenol, can also disrupt electron transport
- Oligomycin binds to the subunit of Fo, blocking the movement of protons through Fo
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Description
This quiz assesses understanding of the relation between equilibrium constant and free energy change, including the impact of temperature on spontaneity of a reaction. It covers bioenergetics and thermodynamics concepts.
