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Questions and Answers
What is the Gibbs free energy change ($, riangle G^ ext{o}'$) for the conversion of ATP to ADP and H3PO4?
What is the Gibbs free energy change ($, riangle G^ ext{o}'$) for the conversion of ATP to ADP and H3PO4?
- -17 kJ/mol
- +14 kJ/mol
- -31 kJ/mol (correct)
- -32.2 kJ/mol
Gibbs energy of the coupled reaction of glucose and ATP is positive.
Gibbs energy of the coupled reaction of glucose and ATP is positive.
False (B)
Name one factor that determines the high $ riangle G$ of ATP hydrolysis.
Name one factor that determines the high $ riangle G$ of ATP hydrolysis.
Electrostatic repulsion
The reaction of __________ and H3PO4 converts glucose to glucose 6-phosphate.
The reaction of __________ and H3PO4 converts glucose to glucose 6-phosphate.
Match the following macroergic compounds with their respective energy release (kJ/mol):
Match the following macroergic compounds with their respective energy release (kJ/mol):
Which of the following describes an isolated system?
Which of the following describes an isolated system?
A heterogenous system has physically uniform parts.
A heterogenous system has physically uniform parts.
What does the equilibrium constant (K) indicate about the composition of a reaction mixture?
What does the equilibrium constant (K) indicate about the composition of a reaction mixture?
In an exothermic reaction, the change in enthalpy (ΔH°) is __________.
In an exothermic reaction, the change in enthalpy (ΔH°) is __________.
Match the following thermodynamic terms with their definitions:
Match the following thermodynamic terms with their definitions:
If K is much greater than 1 (K » 1), what can be inferred about the reaction at equilibrium?
If K is much greater than 1 (K » 1), what can be inferred about the reaction at equilibrium?
According to Le Chatelier's Principle, increasing the pressure will favor the side of the reaction with more gas molecules.
According to Le Chatelier's Principle, increasing the pressure will favor the side of the reaction with more gas molecules.
According to the second law of thermodynamics, what is the general tendency of chemical processes?
According to the second law of thermodynamics, what is the general tendency of chemical processes?
What happens when the temperature increases in an exothermic reaction?
What happens when the temperature increases in an exothermic reaction?
An increase in pressure will shift equilibrium in the direction of NH3 decomposition.
An increase in pressure will shift equilibrium in the direction of NH3 decomposition.
Define chemical equilibrium.
Define chemical equilibrium.
According to the 1st Law of Thermodynamics, energy cannot be created or __________.
According to the 1st Law of Thermodynamics, energy cannot be created or __________.
Match the following concepts with their definitions:
Match the following concepts with their definitions:
What is the effect of adding more substrate on the equilibrium of a reaction producing NH3?
What is the effect of adding more substrate on the equilibrium of a reaction producing NH3?
In dynamic equilibrium, substances stop moving.
In dynamic equilibrium, substances stop moving.
What is required for a dynamic (steady-state) system to maintain constant properties?
What is required for a dynamic (steady-state) system to maintain constant properties?
A decrease in temperature will shift equilibrium in the direction of the __________ reaction.
A decrease in temperature will shift equilibrium in the direction of the __________ reaction.
Which statement is true regarding the total internal energy of an isolated system?
Which statement is true regarding the total internal energy of an isolated system?
What does ΔG represent in the context of the reaction A + B  C + D?
What does ΔG represent in the context of the reaction A + B  C + D?
The standard state of ΔG occurs at a concentration of 1 mol/L and a temperature of 0°C.
The standard state of ΔG occurs at a concentration of 1 mol/L and a temperature of 0°C.
What is the gas constant R used in the Gibbs free energy equation?
What is the gas constant R used in the Gibbs free energy equation?
In living systems, energy can be transformed but cannot be _____ or _____ .
In living systems, energy can be transformed but cannot be _____ or _____ .
Match the following types of work to their functions in living systems:
Match the following types of work to their functions in living systems:
What is the relationship between ΔG and the equilibrium constant K?
What is the relationship between ΔG and the equilibrium constant K?
The 1st Law of Thermodynamics states that energy cannot be transformed into different forms.
The 1st Law of Thermodynamics states that energy cannot be transformed into different forms.
What is the main source of energy for green plants and photosynthesizing bacteria?
What is the main source of energy for green plants and photosynthesizing bacteria?
ΔG° is used to estimate the _____ of the process at standard conditions.
ΔG° is used to estimate the _____ of the process at standard conditions.
Which of the following is NOT a function of the chemical energy obtained from food in organisms?
Which of the following is NOT a function of the chemical energy obtained from food in organisms?
What must occur for the 2nd Law of Thermodynamics to hold true in living systems?
What must occur for the 2nd Law of Thermodynamics to hold true in living systems?
A living cell can maintain a low-entropy state without releasing any energy as heat.
A living cell can maintain a low-entropy state without releasing any energy as heat.
What is the significance of coupling endergonic and exergonic reactions in living systems?
What is the significance of coupling endergonic and exergonic reactions in living systems?
The process of phosphorylating glucose is an example of an ______ reaction.
The process of phosphorylating glucose is an example of an ______ reaction.
Match the following terms with their definitions:
Match the following terms with their definitions:
What is the overall Gibbs free energy change for the reaction: glucose + H3PO4 → glucose 6-phosphate + H2O?
What is the overall Gibbs free energy change for the reaction: glucose + H3PO4 → glucose 6-phosphate + H2O?
Biopolymers have a low value of Gibbs free energy compared to their building blocks.
Biopolymers have a low value of Gibbs free energy compared to their building blocks.
What is an energy carrier in the context of coupled reactions?
What is an energy carrier in the context of coupled reactions?
Higher chemotrophic organisms typically get their energy from ______.
Higher chemotrophic organisms typically get their energy from ______.
Which of the following indicates a reaction is exergonic?
Which of the following indicates a reaction is exergonic?
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Study Notes
Thermodynamics Basics
- Thermodynamics (TD) studies energy relationships in chemical and physical processes.
- State functions include energy (E), pressure (p), temperature (T), and concentration (c); their changes depend on the initial and final states.
Thermodynamic Systems
- Open system: Exchanges both energy and matter with surroundings.
- Closed system: Exchanges energy but not matter.
- Isolated system: Does not exchange energy or matter.
- Homogeneous system: Physically uniform, while heterogeneous systems consist of different parts.
Chemical Equilibrium
- Chemical equilibrium occurs when the rates of forward and reverse reactions are equal, with no observable changes in the mixture.
- Equilibrium constant (K) is defined by concentrations of reactants and products:
[K = \frac{[C]^c[D]^d}{[A]^a[B]^b}] - K values indicate reaction tendencies:
- (K > 1): Product concentration larger than reactants, favors product formation.
- (K \approx 1): Roughly equal concentrations.
- (K < 1): Product concentration lower than reactants, limited reaction extent.
Le Chatelier’s Principle
- Changes in concentration, temperature, or pressure shift equilibrium:
- Concentration: Adding substrate shifts towards products; adding product shifts towards reactants.
- Temperature: Increasing temperature shifts towards endothermic direction; decreasing shifts towards exothermic direction.
- Pressure: Increasing pressure shifts towards fewer gas moles; decreasing shifts towards more gas moles.
Equilibrium vs Steady State
- Chemical Equilibrium: Achieved in isolated systems, concentrations do not change over time.
- Dynamic (Steady-State): Requires energy to maintain constant properties, with continuous substance movement.
Laws of Thermodynamics
- 1st Law: Energy cannot be created or destroyed, only transformed.
- Total internal energy of an isolated system remains constant.
- Gibbs Free Energy (ΔG):
[\Delta G = \Delta G^\circ + RT \ln \left(\frac{[C][D]}{[A][B]}\right)]- At equilibrium: ΔG = 0 and K is defined.
Energy in Living Systems
- Living systems are open systems, exchanging energy and matter with surroundings.
- Energy transformation in organisms:
- Green plants convert light energy to chemical energy.
- Other organisms convert chemical energy from food into biomolecular energy, mechanical work, electrical work, osmotic work, and heat.
Gibbs Free Energy and Biochemistry
- Biopolymers have high Gibbs free energy compared to their building blocks.
- Energy-coupled reactions enable endergonic reactions to occur using exergonic reaction energy.
- Example of coupling:
Glucose phosphorylation (endergonic) coupled with ATP hydrolysis (exergonic) provides an overall negative Gibbs free energy change.
Macroergic Compounds
- Macroergic compounds release large amounts of energy:
- Phosphoenolpyruvate: -61.9 kJ/mol
- 1,3-bisphosphoglycerate: -49.3 kJ/mol
- ATP hydrolysis contributes:
- ATP → ADP + Pi: -32.2 kJ/mol
- ATP → AMP + PPi: -30.5 kJ/mol
ATP and Energy Transfer
- ATP is crucial for energy transfer in living systems, with continuous cleavage and recovery.
- High ΔG of ATP hydrolysis results from electrostatic repulsion, resonance stability, and increased disorder (ΔS > 0) due to ionization.
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