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Questions and Answers
What does the First Law of Thermodynamics state?
What does the First Law of Thermodynamics state?
- Energy transfer is always 100% efficient.
- All forms of energy are interchangeable without loss.
- Energy of the universe is constant. (correct)
- Energy can be created and destroyed.
What is meant by the term 'entropy'?
What is meant by the term 'entropy'?
- The total energy content of a system.
- The amount of useful work obtained from energy.
- The heat produced during chemical reactions.
- The degree of order or randomness in a system. (correct)
What characterizes an exergonic reaction?
What characterizes an exergonic reaction?
- It requires energy input to proceed.
- It is spontaneous with a net release of free energy. (correct)
- The change in Gibbs free energy (∆G) is positive.
- It results in the formation of high-energy products.
How does the Second Law of Thermodynamics relate to energy transformations?
How does the Second Law of Thermodynamics relate to energy transformations?
In which process does entropy not change according to reversible processes?
In which process does entropy not change according to reversible processes?
What happens to entropy during irreversible processes?
What happens to entropy during irreversible processes?
What is the relationship between Gibbs free energy (∆G) and endergonic reactions?
What is the relationship between Gibbs free energy (∆G) and endergonic reactions?
How is enthalpy defined?
How is enthalpy defined?
What does a negative change in Gibbs free energy (ΔG < 0) indicate about a reaction?
What does a negative change in Gibbs free energy (ΔG < 0) indicate about a reaction?
Which of the following correctly describes an endergonic reaction?
Which of the following correctly describes an endergonic reaction?
What occurs when an endergonic reaction is coupled with an exergonic reaction?
What occurs when an endergonic reaction is coupled with an exergonic reaction?
In standard biochemical conditions, what is the pH level typically assumed for Gibbs free energy calculations?
In standard biochemical conditions, what is the pH level typically assumed for Gibbs free energy calculations?
For the reaction: Glucose + ATP → glucose-6-phosphate + ADP + Pi, what is the overall change in Gibbs free energy (ΔG)?
For the reaction: Glucose + ATP → glucose-6-phosphate + ADP + Pi, what is the overall change in Gibbs free energy (ΔG)?
Under standard biochemical conditions, what is the pressure assumed for Gibbs free energy calculations?
Under standard biochemical conditions, what is the pressure assumed for Gibbs free energy calculations?
If a reaction is exergonic in one direction, what can be inferred about its reverse reaction?
If a reaction is exergonic in one direction, what can be inferred about its reverse reaction?
Which statement correctly describes Gibbs free energy?
Which statement correctly describes Gibbs free energy?
Flashcards
First Law of Thermodynamics
First Law of Thermodynamics
Energy cannot be created or destroyed, only transformed.
Entropy
Entropy
A measure of disorder and randomness in a system.
Enthalpy
Enthalpy
Total heat content of a system; internal energy plus pressure-volume product.
Second Law of Thermodynamics
Second Law of Thermodynamics
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Exergonic Reaction
Exergonic Reaction
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Endergonic Reaction
Endergonic Reaction
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Equilibrium in Reactions
Equilibrium in Reactions
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Irreversible Processes
Irreversible Processes
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Gibbs Free Energy
Gibbs Free Energy
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ΔG
ΔG
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Coupled Reactions
Coupled Reactions
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Standard Biochemical Conditions
Standard Biochemical Conditions
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Energy Change Direction
Energy Change Direction
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Free Energy Changes
Free Energy Changes
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Study Notes
Thermodynamics and Reactions
- Thermodynamics describes energy transformations in the universe.
- The first law of thermodynamics states that energy cannot be created or destroyed, only transferred or transformed. It's also called the principle of conservation of energy.
- Entropy is a thermodynamic property representing the unavailability of a system's energy for useful work. It's often related to disorder.
- Enthalpy is the total heat content of a system, equal to internal energy plus the product of pressure and volume.
- The second law of thermodynamics states that every energy transfer or transformation increases the entropy of the universe. Energy transfer isn't 100% efficient. Some energy is always lost as heat. For instance, photosynthesis and oxidation of glucose are only about 42% efficient.
- Systems tend toward higher entropy (more disorder). Reversible processes keep the entropy of the system and surroundings unchanged.
Exergonic vs. Endergonic Reactions
- Exergonic reactions release energy, and are spontaneous, meaning they occur without external input
- Endergonic reactions absorb energy from their surroundings; they are non-spontaneous
- The change in Gibbs free energy (ΔG) determines if a reaction is spontaneous.
- ΔG < 0 for exergonic reactions.
- ΔG > 0 for endergonic reactions.
- ΔG = 0 for reactions at equilibrium, which means there is no net change in the reaction.
- Gibbs free energy (G) is a measure of energy available to do useful work.
- Reactions are often coupled (linked) to enable reactions to occur (energy release is harnessed for energy absorption)
ATP
- ATP (adenosine triphosphate) is the energy currency of cells.
- ATP is constantly formed and broken down in cells.
- ATP stores free energy in high-energy phosphate bonds.
- These bonds form when 2 phosphoric acids or carboxylic and phosphoric acids split out water
- ATP hydrolysis (breaking down ATP) releases energy. This energy is used to drive a variety of (endergonic) processes.
- Energy from exergonic reactions (like cellular respiration) is used to produce ATP from ADP (adenosine diphosphate) and inorganic phosphate (Pi).
- ATP, therefore, is a key molecule for coupling exergonic and endergonic reactions.
- Coupled reactions allow for endergonic reactions to occur and are essential for various processes, including biosynthesis.
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