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Questions and Answers
The reaction $C_6H_{12}O_6 + 6O_2 \rightarrow 6CO_2 + 6H_2O$ has a $\Delta G = -686$ kcal/mole. What does this indicate about the reaction?
The reaction $C_6H_{12}O_6 + 6O_2 \rightarrow 6CO_2 + 6H_2O$ has a $\Delta G = -686$ kcal/mole. What does this indicate about the reaction?
- The reaction is spontaneous and releases energy. (correct)
- The reaction requires energy input to proceed.
- The reaction will not occur without enzyme catalysis.
- The reaction is at equilibrium.
Why doesn't all the sugar in your cells spontaneously break down to release energy, even though cellular respiration has a large negative $\Delta G$?
Why doesn't all the sugar in your cells spontaneously break down to release energy, even though cellular respiration has a large negative $\Delta G$?
- The concentration of sugar in cells is too low for the reaction to occur spontaneously.
- The reaction is thermodynamically unfavorable.
- The reaction requires an input of energy to overcome the activation energy. (correct)
- The reaction is endergonic under cellular conditions.
How do enzymes affect the overall change in free energy ($\Delta G$) of a reaction?
How do enzymes affect the overall change in free energy ($\Delta G$) of a reaction?
- Enzymes increase the overall $\Delta G$ of the reaction, making it more exergonic.
- Enzymes can either increase or decrease the overall $\Delta G$, depending on the specific reaction.
- Enzymes decrease the overall $\Delta G$ of the reaction, making it more endergonic.
- Enzymes have no impact on the overall $\Delta G$ of the reaction. (correct)
Which of the following is NOT a mechanism by which enzymes catalyze reactions?
Which of the following is NOT a mechanism by which enzymes catalyze reactions?
During the enzyme cycle, what happens to the enzyme at the end of the catalytic cycle?
During the enzyme cycle, what happens to the enzyme at the end of the catalytic cycle?
The specificity of an enzyme for its substrate is primarily determined by:
The specificity of an enzyme for its substrate is primarily determined by:
Magnesium is required for chlorophyll function. What role does magnesium play in this process?
Magnesium is required for chlorophyll function. What role does magnesium play in this process?
How can you experimentally distinguish between a competitive and a non-competitive inhibitor?
How can you experimentally distinguish between a competitive and a non-competitive inhibitor?
Which of the following best describes the relationship between entropy and free energy in a system, assuming temperature remains constant?
Which of the following best describes the relationship between entropy and free energy in a system, assuming temperature remains constant?
Consider a chemical reaction where the change in enthalpy (ΔH) is positive and the change in entropy (ΔS) is negative. Under what conditions, if any, will this reaction be spontaneous?
Consider a chemical reaction where the change in enthalpy (ΔH) is positive and the change in entropy (ΔS) is negative. Under what conditions, if any, will this reaction be spontaneous?
In the context of thermodynamics, which statement accurately describes the first law of thermodynamics?
In the context of thermodynamics, which statement accurately describes the first law of thermodynamics?
An exergonic reaction is characterized by which of the following?
An exergonic reaction is characterized by which of the following?
A cell performing active transport moves a substance against its concentration gradient. Which statement is true regarding the change in free energy (ΔG) for this process and its classification?
A cell performing active transport moves a substance against its concentration gradient. Which statement is true regarding the change in free energy (ΔG) for this process and its classification?
Why does diffusion, the movement of molecules from an area of high concentration to an area of low concentration, have a negative change in free energy (-ΔG)?
Why does diffusion, the movement of molecules from an area of high concentration to an area of low concentration, have a negative change in free energy (-ΔG)?
In a biological system, an endergonic reaction can be 'driven' by coupling it with an exergonic reaction. What is the most important reason for this coupling?
In a biological system, an endergonic reaction can be 'driven' by coupling it with an exergonic reaction. What is the most important reason for this coupling?
Consider a scenario where intestinal cells actively transport glucose from the intestinal lumen, where the glucose concentration is low, into the cell, where the glucose concentration is high. What can be inferred about the overall change in Gibbs free energy (ΔG) for this import process?
Consider a scenario where intestinal cells actively transport glucose from the intestinal lumen, where the glucose concentration is low, into the cell, where the glucose concentration is high. What can be inferred about the overall change in Gibbs free energy (ΔG) for this import process?
A chemical reaction has a positive enthalpy change ($ΔH > 0$) and a decrease in entropy ($ΔS < 0$). Based on the Gibbs free energy equation, $\Delta G = \Delta H - T\Delta S$, which of the following is always true regarding the spontaneity of this reaction?
A chemical reaction has a positive enthalpy change ($ΔH > 0$) and a decrease in entropy ($ΔS < 0$). Based on the Gibbs free energy equation, $\Delta G = \Delta H - T\Delta S$, which of the following is always true regarding the spontaneity of this reaction?
An enzyme is functioning at its optimal temperature and pH. Which of the following scenarios would lead to the greatest increase in the rate of product formation?
An enzyme is functioning at its optimal temperature and pH. Which of the following scenarios would lead to the greatest increase in the rate of product formation?
Consider an enzyme-catalyzed reaction where the substrate concentration is significantly higher than the enzyme concentration. What effect will the addition of more substrate have on the reaction rate?
Consider an enzyme-catalyzed reaction where the substrate concentration is significantly higher than the enzyme concentration. What effect will the addition of more substrate have on the reaction rate?
Imagine a scientist discovers a new enzyme. They perform experiments and find that the enzyme activity is significantly reduced in the presence of a specific molecule, but only when the molecule binds to a site distinct from the active site. This is most likely an example of:
Imagine a scientist discovers a new enzyme. They perform experiments and find that the enzyme activity is significantly reduced in the presence of a specific molecule, but only when the molecule binds to a site distinct from the active site. This is most likely an example of:
Two reactions are coupled, where an exergonic reaction ($\Delta G_1 < 0$) provides the energy for an endergonic reaction ($\Delta G_2 > 0$). For the coupled reaction to be spontaneous overall, which of the following conditions must be met?
Two reactions are coupled, where an exergonic reaction ($\Delta G_1 < 0$) provides the energy for an endergonic reaction ($\Delta G_2 > 0$). For the coupled reaction to be spontaneous overall, which of the following conditions must be met?
Flashcards
Energy
Energy
The capacity to do work.
Kinetic Energy
Kinetic Energy
Energy of motion.
Potential Energy
Potential Energy
Stored energy due to location or arrangement (e.g., chemical energy).
Thermodynamics
Thermodynamics
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1st Law of Thermodynamics
1st Law of Thermodynamics
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2nd Law of Thermodynamics
2nd Law of Thermodynamics
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Free Energy
Free Energy
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Exergonic Reaction
Exergonic Reaction
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dG (Gibbs Free Energy)
dG (Gibbs Free Energy)
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Activation Energy
Activation Energy
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Enzymes
Enzymes
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Enzyme Active Site
Enzyme Active Site
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Enzyme Inhibitors
Enzyme Inhibitors
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Competitive Inhibitor
Competitive Inhibitor
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Free Energy (∆G)
Free Energy (∆G)
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Transition State
Transition State
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Catalytic Cycle
Catalytic Cycle
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Noncompetitive Inhibition
Noncompetitive Inhibition
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Study Notes
- Energy is the capacity to do work.
- Kinetic energy is the energy of motion.
- Potential energy is stored energy due to location or arrangement, such as chemical energy.
- Energy can be converted, transferred, or transformed but is never 100% efficient, resulting in heat loss.
Thermodynamics
- Thermodynamics is the study of energy transformations in a collection of matter (system).
- The 1st Law of Thermodynamics states that energy is conserved; it can be transferred or transformed but not destroyed (Principle of the Conservation of Energy).
- The 2nd Law of Thermodynamics states that every energy transfer or transformation increases the disorder (entropy) of the universe.
Free Energy
- Free energy is the portion of a system's energy available to do work.
- The formula for Gibbs Free Energy is G = H - TS, where:
- H is enthalpy or total energy in a system.
- T is temperature (measure of kinetic energy).
- S is entropy (measure of disorder).
- As entropy increases, the amount of energy available to do work decreases.
- There's a general tendency to move to a lower energy state, which is more stable.
- When tracking energy transfer or transformation, the change in free energy (ΔG) is calculated as ΔG = ΔH - TΔS.
- If ΔG is negative, free energy is decreased, energy is released, and it is an exergonic and spontaneous reaction.
Concentration Gradients
- Potential energy in a concentration gradient can be released or transferred.
- Diffusion releases potential energy in a concentration gradient and is a spontaneous reaction.
- Intestine cells bring glucose in from the intestinal lumen even when the glucose concentration is higher in the cells.
- Processes that move substances against their concentration gradients require energy and have a +ΔG, which are endergonic.
- Cells use mechanisms like the Sodium-Potassium Pump to move ions against their concentration gradients.
- Cellular respiration has a high negative ΔG.
- Glucose + 6 O₂ yields 6 CO₂ + 6 H₂O with ΔG = -686 kcal/mole, and is exergonic.
Activation Energy
- Even though a reaction has a negative ΔG, it requires energy (activation energy) to reach a transition state.
- Enzymes are required to catalyze reactions.
- Enzymes lower the activation energy required for a reaction.
- Enzymes do not affect the overall ΔG for the reaction.
- Enzymes lower activation energy by:
- Holding substrates in proximity or proper orientation
- Straining and distorting bonds
- Providing the suitable local environment for the reaction
- Acting through transient covalent bonds as part of an intermediate
Enzyme Cycle
- Enzymes bind specifically to an active site.
- Substrate binding can temporarily change enzyme structure (induced fit).
- Enzymes are unchanged at the end of the catalytic cycle.
- Specific binding relies on the chemical characteristics and positioning of R-groups of the amino acids at the active site.
Factors Affecting Enzyme Reaction Rate
- Substrate concentration
- Temperature
- pH
- Coenzymes: additional molecules/atoms function as part of the enzyme.
- Magnesium is a cofactor for chlorophyll.
- Iron is for hemoglobin.
- Two cofactors, NADH and FADH2, function as necessary coenzymes in respiration.
Enzyme Inhibitors
- Other molecules can act as regulators to affect the functioning of the enzyme.
- Two types of inhibitors are competitive and non-competitive inhibitors.
- Allosteric regulation of enzymes involves multi-subunit enzymes with allosteric activators and inhibitors.
- Feedback inhibition occurs when the end product of a metabolic pathway inhibits an earlier step in the pathway.
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Description
Explore the roles of energy, thermodynamics, and free energy in physical systems. Understand the laws of thermodynamics, including energy conservation and entropy increase. Learn how free energy is used to determine the energy available to do work, as well as the Gibbs Free Energy Equation.
