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Questions and Answers
What is the name of the thermodynamic quantity that represents the unavailable thermal energy for conversion into mechanical work?
What is the name of the thermodynamic quantity that represents the unavailable thermal energy for conversion into mechanical work?
According to the first law of thermodynamics, which of these statements is TRUE?
According to the first law of thermodynamics, which of these statements is TRUE?
Which of the following statements correctly describes an exergonic reaction?
Which of the following statements correctly describes an exergonic reaction?
Which of the following scenarios represents an increase in entropy?
Which of the following scenarios represents an increase in entropy?
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What is the thermodynamic quantity that represents the total heat content of a system?
What is the thermodynamic quantity that represents the total heat content of a system?
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What is the change in free energy for a reaction at equilibrium?
What is the change in free energy for a reaction at equilibrium?
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Which of the following is NOT a true statement about the second law of thermodynamics?
Which of the following is NOT a true statement about the second law of thermodynamics?
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What is the main reason why cells expend energy to maintain their structure and organization?
What is the main reason why cells expend energy to maintain their structure and organization?
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Which of the following statements accurately describes the relationship between endergonic and exergonic reactions?
Which of the following statements accurately describes the relationship between endergonic and exergonic reactions?
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What is the change in Gibbs free energy (ΔG) for the following reaction: Glucose + ATP → glucose-6-phosphate + ADP + Pi?
What is the change in Gibbs free energy (ΔG) for the following reaction: Glucose + ATP → glucose-6-phosphate + ADP + Pi?
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What is the meaning of the concept 'usable energy' in the context of Gibbs free energy?
What is the meaning of the concept 'usable energy' in the context of Gibbs free energy?
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What is the sign convention for ΔG in an exergonic reaction?
What is the sign convention for ΔG in an exergonic reaction?
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Which of the following is a standard condition for biochemical reactions?
Which of the following is a standard condition for biochemical reactions?
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What is the relationship between the direction of a reaction and the sign of ΔG?
What is the relationship between the direction of a reaction and the sign of ΔG?
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What does the term 'coupled reactions' refer to in the context of biochemical reactions?
What does the term 'coupled reactions' refer to in the context of biochemical reactions?
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A reaction with a ΔG of +5 kcal/mol is considered:
A reaction with a ΔG of +5 kcal/mol is considered:
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Flashcards
First Law of Thermodynamics
First Law of Thermodynamics
Energy cannot be created or destroyed, only transformed or transferred.
Entropy
Entropy
A measure of disorder or randomness in a system; higher entropy means more disorder.
Enthalpy
Enthalpy
Total heat content of a system, equal to internal energy plus pressure-volume work.
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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ΔG = 0
ΔG = 0
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Energy Transformation
Energy Transformation
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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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Glycolysis Example
Glycolysis Example
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Energy Requirement vs. Release
Energy Requirement vs. Release
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Study Notes
Thermodynamics
- The laws of thermodynamics describe energy transformations in the universe.
First Law of Thermodynamics
- The energy of the universe is constant.
- Energy can be transferred or transformed, but not created or destroyed.
- Also known as the principle of conservation of energy.
- Entropy: a thermodynamic quantity representing the unavailability of a system's thermal energy for conversion into mechanical work, often interpreted as the degree of disorder or randomness in the system.
- Enthalpy: a thermodynamic quantity equivalent to the total heat content of a system. It is equal to the internal energy of the system plus the product of pressure and volume.
Second Law of Thermodynamics
- During energy transfer or transformation, some energy is unusable and often lost as heat.
- 100% efficiency of energy transfer is impossible.
- Many important biological processes (e.g., photosynthesis, oxidation of glucose) have efficiencies around 42%.
- Every energy transfer or transformation increases the entropy (disorder) of the universe.
- Entropy is a measure of disorder and randomness in a system (or its surroundings).
Systems and Entropy
- Systems tend to proceed from ordered (low-entropy) states to disordered (high-entropy) states.
- The entropy of the system plus surroundings is unchanged by reversible processes.
- The entropy of the system plus surroundings increases for irreversible processes.
Spontaneous Reactions
- Spontaneous reactions occur as time passes.
- Organized effort requires energy input (e.g., cleaning a room).
- Cells use energy to resist the natural tendency toward disorder and maintain structure.
Exergonic and Endergonic Reactions
- Exergonic reactions release free energy.
- ΔG is negative.
- Spontaneous reactions.
- Endergonic reactions absorb free energy.
- ΔG is positive.
- Non-spontaneous reactions.
- If ΔG = 0, the reaction is at equilibrium, with no net flow in either direction.
Gibbs Free Energy
- Gibbs free energy is a measure of usable energy in a system.
- ΔG = change in Gibbs free energy = Gfinal - Ginitial
- Activation energy: energy needed to initiate a reaction.
- Catalysts: substances that reduce the activation energy of a reaction.
Reaction Diagrams
- Exergonic reactions: energy released, reactants higher in energy
- Endergonic reactions: energy absorbed, reactants lower in energy
Coupling Reactions and ATP
- Endergonic reactions are often coupled with exergonic reactions to proceed.
- ATP hydrolysis: ATP is converted to ADP + Pi, releasing energy.
- ATP synthesis: ADP + Pi are combined to reform ATP, requiring energy.
- ATP is the energy currency of the cell.
ATP Role
- Transfer of chemical energy.
- Stored energy.
- Energy currency
- ATP structure: Adenosine triphosphate containing 3 phosphate groups.
- Phosphoanhydride bonds are formed by splitting out water between 2 phosphoric acids or between carboxylic & phosphoric acids. They have a large negative ΔG of hydrolysis, releasing energy when broken down
- Hydrolysis of ATP must be coupled with an endergonic process to drive it forward.
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Description
Test your understanding of key concepts in thermodynamics, including thermodynamic quantities, laws, and energy conversions. This quiz covers topics such as Gibbs free energy, entropy, and exergonic vs. endergonic reactions. Perfect for students studying physics or chemistry!
