6: Thermodynamics

Students calculate delta G and Keq, determine whether reactions are spontaneous, and interpret free energy diagrams for enzyme-catalyzed reactions.

LibreTexts reference: Unit 2, Chapter 1: Enzyme Thermodynamics

Matching Energy Terms to Requirement Categories

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Match each energy requirement category with its corresponding energy term.

Note: Each choice will be used exactly once.

	Your Choice	Prompt
	Drop Your Choice Here	1. requires energy input
	Drop Your Choice Here	2. releases energy

Drag one of the choices below:

• A. ΔG < 0
• B. bio-synthesis

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Matching Enzyme Catalysis Terms to Definitions

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Match each of the following terms related to enzyme catalysis with their corresponding definitions.
Note: Each choice will be used exactly once.

	Your Choice	Prompt
	Drop Your Choice Here	1. Ligand
	Drop Your Choice Here	2. Reactant
	Drop Your Choice Here	3. Substrate
	Drop Your Choice Here	4. Reagent

Drag one of the choices below:

• A. a molecule that facilitates a chemical reaction
• B. substance that is transformed into one or more chemical products.
• C. any substance that forms a complex with a biomolecule to serve a biological purpose
• D. a molecule that is transformed into a product by an enzyme

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True/False Statements About Chemical Reactions

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Which one of the following statements is TRUE concerning chemical reactions?

• A. For chemical reactions to happen, the chemical identity of both reactants and products remains the same.
• B. Chemical reactions only occur when energy is added.
• C. Chemical reactions are involved in many important processes in biology.
• D. Chemical reactions only occur in the presence of light.
• E. Chemical reactions are always endothermic.

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True/False Statements About Enzyme Cofactors

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Which one of the following molecular entities CANNOT be classified as an enzymatic cofactor?

• A. the glycolysis enzyme, hexokinase
• B. progesterone (P4), a steroid hormone involved in the menstrual cycle
• C. vitamin B₁, thiamin
• D. creatine, an organic molecule that recharges ATP
• E. adenosine diphosphate (ADP)

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True/False Statements About Enzyme Equilibrium and Kinetics

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Which one of the following statements is FALSE concerning enzyme kinetics?

• A. enzymes cannot change the standard free energy (ΔG°′) of a chemical reaction
• B. enzymes cannot change the equilibrium of the chemical reaction
• C. enzymes can provide favorable microenvironments for a chemical reaction
• D. enzymes lower the activation energy of a chemical reaction
• E. enzymes reduce the rate of a chemical reaction

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True/False Statements About Gibbs Free Energy (Delta G = Delta H - T Delta S)

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Which one of the following statements is FALSE about the Gibbs free energy, ΔG = ΔH – TΔS?

• A. When ΔG = 0 the reaction has reached equilibrium
• B. ΔS is the change in entropy
• C. enthalpy is associated with the heat content of a system
• D. When ΔS < 0 the reaction is called non-spontaneous
• E. Negative enthalpy makes a reaction more favorable

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True/False Statements About Potential and Kinetic Energy

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Which one of the following is an example of potential energy rather than kinetic energy?

• A. molecules of glucose swirling around in a glass of water
• B. wet clothes in the washer during the spin cycle
• C. a skier at the top of a hill
• D. a hammer striking a nail
• E. a car speeding on the interstate

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True/False Statements About Thermodynamics and Kinetics

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Which one of the following statements is FALSE of thermodynamics and kinetics?

• A. In general, more disorder means less entropy.
• B. The second law of thermodynamics states that the total entropy of a closed system will always increase.
• C. Enzymes increase or decrease the rate of a reaction.
• D. The change in Gibbs free energy (ΔG) of a reaction is related to the enthalpy and entropy changes of the reaction.
• E. Thermodynamics determines the direction a reaction will proceed under specific conditions.

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True/False Statements About Enzyme Naming Patterns

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Enzymes are biological catalysts that speed up chemical reactions in living organisms.
Which one of the following choices is most likely an enzyme?
Hint: enzymes often have a distinct naming pattern that can help identify them.

• A. carbon dioxide (CO₂)
• B. triacylglycerol
• C. NADH
• D. testosterone
• E. adenylyl cyclase

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Energy Requirement Categories from Energy Terms

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Which one of the following energy requirement categories correspond to the energy term 'polymer breakdown'.

• A. releases energy
• B. requires energy input

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Enzyme Catalysis Terms from Definitions

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Which one of the following terms related to enzyme catalysis correspond to the definition 'enzyme without its cofactors'.

• A. Apoenzyme
• B. Ligand-binding site
• C. Product
• D. Substrate

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Biochemical vs Chemical Standard Free Energy States

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ΔG°′ (delta G naught-prime, ΔG°′) adjusts the standard state conditions used in ΔG° (delta G naught, ΔG°). What does it adjust?

• A. pH is fixed at 7 ([H⁺] = 1 × 10⁻⁷ M instead of 1 M)
• B. temperature is different from 298 K (25 °C)
• C. pressure is different from 1 atm
• D. all reactant concentrations are at 1 M
• E. volume of the system is standardized to 1 liter

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Exergonic and Endergonic Reaction Classification

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A reaction is classified as exergonic. Which statement about ΔG is true?

• A. ΔG = 0 (the reaction is at equilibrium)
• B. ΔG < 0 (negative)
• C. no activation energy is required for this reaction
• D. ΔG > 0 (positive)

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Gibbs Free Energy Change and Equilibrium Constant Relationships

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If the standard transformed Gibbs free energy change (ΔG°′) is positive (greater than zero), what is the value of the equilibrium constant (K′_eq) relative to 1?

• A. less than 1
• B. equal to 1
• C. greater than 1

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Gibbs Free Energy Equation Symbols and Meanings

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The Gibbs free energy equation is ΔG = ΔH − TΔS. Match each symbol to its meaning.

	Your Choice	Prompt
	Drop Your Choice Here	1. ΔS
	Drop Your Choice Here	2. ΔG
	Drop Your Choice Here	3. ΔH
	Drop Your Choice Here	4. T

Drag one of the choices below:

• A. absolute temperature (Kelvin)
• B. change in enthalpy
• C. change in entropy
• D. change in Gibbs free energy

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Thermodynamics Law Statements

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Select the statement that matches the First Law of Thermodynamics.

• A. entropy of the system always increases for a spontaneous process
• B. entropy of the universe is constant
• C. the total entropy of a system and its surroundings increases for a spontaneous process
• D. the total energy of a system and its surroundings is constant

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First and Second Laws of Thermodynamics for Different Systems

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According to the first law of thermodynamics, the total energy of a closed system is:

• A. always zero
• B. always increasing
• C. always decreasing
• D. always constant (conserved)
• E. cannot be determined without more information

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