Podcast
Questions and Answers
What is the initial energy required to start a chemical reaction called?
What is the initial energy required to start a chemical reaction called?
- Activation energy (correct)
- Free energy change
- Thermal energy
- Bond energy
How do enzymes affect chemical reactions?
How do enzymes affect chemical reactions?
- They convert the products into reactants.
- They lower the activation energy barrier. (correct)
- They alter the reactants involved in the reaction.
- They increase the reaction's free energy change.
What form of energy is often supplied to reactants to overcome the activation energy barrier?
What form of energy is often supplied to reactants to overcome the activation energy barrier?
- Electrical energy
- Thermal energy (correct)
- Nuclear energy
- Chemical energy
What is indicated by the symbol ∆G in a chemical reaction?
What is indicated by the symbol ∆G in a chemical reaction?
What is true about the effect of enzymes on the energy profile of a reaction?
What is true about the effect of enzymes on the energy profile of a reaction?
What is the optimal temperature for a typical human enzyme?
What is the optimal temperature for a typical human enzyme?
Which of the following is a characteristic of cofactors?
Which of the following is a characteristic of cofactors?
Which enzyme has an optimal pH in the stomach?
Which enzyme has an optimal pH in the stomach?
What type of inhibitor binds to the active site of an enzyme?
What type of inhibitor binds to the active site of an enzyme?
Which of the following statements is true about coenzymes?
Which of the following statements is true about coenzymes?
What effect do noncompetitive inhibitors have on enzymes?
What effect do noncompetitive inhibitors have on enzymes?
What is the optimal temperature for the enzyme of thermophilic bacteria?
What is the optimal temperature for the enzyme of thermophilic bacteria?
Which of the following is an example of enzyme inhibitors?
Which of the following is an example of enzyme inhibitors?
What happens to the entropy of the universe during every energy transfer or transformation?
What happens to the entropy of the universe during every energy transfer or transformation?
What does a negative free-energy change (∆G) indicate about a chemical reaction?
What does a negative free-energy change (∆G) indicate about a chemical reaction?
Which of the following statements is true regarding the second law of thermodynamics?
Which of the following statements is true regarding the second law of thermodynamics?
In the context of free energy, what does the term 'free energy' (G) represent?
In the context of free energy, what does the term 'free energy' (G) represent?
Which equation shows the relationship between changes in free energy, enthalpy, and entropy?
Which equation shows the relationship between changes in free energy, enthalpy, and entropy?
Why do biologists study free-energy changes in reactions?
Why do biologists study free-energy changes in reactions?
What aspect of energy transformations is emphasized in the second law of thermodynamics?
What aspect of energy transformations is emphasized in the second law of thermodynamics?
When considering a spontaneous process, which of the following must be true?
When considering a spontaneous process, which of the following must be true?
What is the primary role of isoleucine in the feedback inhibition of threonine synthesis?
What is the primary role of isoleucine in the feedback inhibition of threonine synthesis?
In the context of feedback inhibition, what happens when isoleucine is used up by the cell?
In the context of feedback inhibition, what happens when isoleucine is used up by the cell?
What is a potential consequence of feedback inhibition in metabolic pathways?
What is a potential consequence of feedback inhibition in metabolic pathways?
Where are enzymes for cellular respiration primarily located in eukaryotic cells?
Where are enzymes for cellular respiration primarily located in eukaryotic cells?
What best describes the role of structures within the cell regarding metabolic pathways?
What best describes the role of structures within the cell regarding metabolic pathways?
What happens to the active site of enzyme 1 during feedback inhibition when isoleucine binds?
What happens to the active site of enzyme 1 during feedback inhibition when isoleucine binds?
What is the significance of enzyme localization within different organelles?
What is the significance of enzyme localization within different organelles?
Which intermediate is formed directly by the enzymatic activity of enzyme 1?
Which intermediate is formed directly by the enzymatic activity of enzyme 1?
What does an enzyme do to the activation energy of a reaction?
What does an enzyme do to the activation energy of a reaction?
What is formed when an enzyme binds to its substrate?
What is formed when an enzyme binds to its substrate?
What is the primary role of the active site in an enzyme?
What is the primary role of the active site in an enzyme?
Which of the following describes the process that helps an enzyme to catalyze a reaction?
Which of the following describes the process that helps an enzyme to catalyze a reaction?
How can an active site enhance reaction catalysis?
How can an active site enhance reaction catalysis?
Which of the following statements about enzymes is FALSE?
Which of the following statements about enzymes is FALSE?
What is one way that the active site of an enzyme lowers the activation energy?
What is one way that the active site of an enzyme lowers the activation energy?
What remains unchanged after an enzymatic reaction?
What remains unchanged after an enzymatic reaction?
Study Notes
Second Law of Thermodynamics
- Every energy transfer or transformation results in some unusable energy, often lost as heat
- Increases entropy (disorder) of the universe
- Evolution of complex organisms doesn't violate the second law
- An organism's entropy might decrease, but the universe's overall entropy increases
Free-Energy Change
- A living system's free energy is energy capable of doing work under uniform temperature and pressure (like a living cell)
- ΔG represents the change in free energy during a process
- Related to:
- ΔH: change in total energy
- ΔS: change in entropy
- T: temperature in Kelvin
- Formula: ΔG = ΔH – TΔS
- Only negative ΔG indicates spontaneous processes
- Spontaneous processes can be harnessed for work
Activation Energy
- Every chemical reaction involves bond breaking and forming
- Activation energy (EA) is the initial energy required to start a chemical reaction
- Often supplied as thermal energy absorbed by reactant molecules from surroundings
Enzymes Lowering the EA Barrier
- Enzymes are biological catalysts that speed up reactions by lowering the EA barrier
- They don't affect the change in free energy (ΔG), but hasten reactions that would eventually occur
Enzyme Substrate Specificity
- The reactant an enzyme acts on is its substrate
- Enzyme binds to substrate forming an enzyme-substrate complex
- The active site is the region on the enzyme where the substrate binds
- Induced fit of a substrate positions active site chemical groups to enhance catalysis
Catalysis in the Enzyme's Active Site
- Substrate binds to the enzyme's active site
- The active site lowers the EA barrier by:
- Orienting substrates correctly
- Straining substrate bonds
- Providing a favorable microenvironment
- Covalently bonding to the substrate
Enzyme Activity Factors: Temperature and pH
- Each enzyme has an optimal temperature for activity (e.g., 37°C for typical human enzyme)
- Optimal pH varies per enzyme (e.g., pepsin in the stomach vs. trypsin in the intestines)
Cofactors
- Nonprotein enzyme helpers
- Can be either inorganic (e.g., metal ions) or organic
- Organic cofactors are called coenzymes
- Vitamins are examples of coenzymes
Enzyme Inhibitors
- Competitive inhibitors bind to the active site, competing with the substrate
- Noncompetitive inhibitors bind elsewhere, causing the enzyme to change shape and reducing active site effectiveness
- Examples include toxins, poisons, pesticides, and antibiotics
Feedback Inhibition
- Regulates metabolic pathways by preventing overproduction of end products
- The end product acts as an inhibitor to an earlier enzyme in the pathway, halting further product synthesis
Specific Localization of Enzymes
- Cellular structures organize metabolic pathways
- Some enzymes are structural components in membranes
- Eukaryotic cells have enzymes in specific organelles (e.g., cellular respiration enzymes in mitochondria)
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Description
Test your understanding of the Second Law of Thermodynamics, free-energy change, and activation energy. This quiz covers key concepts such as entropy, free energy calculations, and the role of activation energy in chemical reactions. Perfect for students studying thermodynamics in biology or chemistry.
