Textbook Question
What energy requirements must be met in order for a reaction to be favorable?
Ch.21 The Generation of Biochemical Energy
McMurry8th EditionFundamentals of General, Organic, and Biological ChemistryISBN: 9780134015187
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Table of contents
- Ch.1 Matter and Measurements27
- Ch.2 Atoms and the Periodic Table20
- Ch.3 Ionic Compounds8
- Ch.4 Molecular Compounds23
- Ch.5 Classification & Balancing of Chemical Reactions12
- Ch.6 Chemical Reactions: Mole and Mass Relationships28
- Ch.7 Chemical Reactions: Energy, Rate and Equilibrium64
- Ch.8 Gases, Liquids and Solids24
- Ch.9 Solutions52
- Ch.10 Acids and Bases25
- Ch.11 Nuclear Chemistry22
- Ch.12 Introduction to Organic Chemistry: Alkanes57
- Ch.13 Alkenes, Alkynes, and Aromatic Compounds47
- Ch.14 Some Compounds with Oxygen, Sulfur, or a Halogen50
- Ch.15 Aldehydes and Ketones45
- Ch.16 Amines42
- Ch.17 Carboxylic Acids and Their Derivatives57
- Ch.18 Amino Acids and Proteins82
- Ch.19 Enzymes and Vitamins63
- Ch.20 Carbohydrates44
- Ch.21 The Generation of Biochemical Energy65
- Ch.22 Carbohydrate Metabolism45
- Ch.23 Lipids42
- Ch.24 Lipid Metabolism33
- Ch.25 Protein and Amino Acid Metabolism24
- Ch.26 Nucleic Acids and Protein Synthesis45
McMurry8th EditionFundamentals of General, Organic, and Biological ChemistryISBN: 9780134015187Not the one you use?Change textbook
Chapter 21, Problem 31c
The following reactions occur during the catabolism of acetyl-CoA. Which are exergonic? Which is endergonic? Which reaction produces a phosphate that later yields energy by giving up a phosphate group?
c. L-Malate + NAD+ → Oxaloacetate + NADH + H+
∆G = +17 kcal/mol (+129.3 kJ/mol)
Verified step by step guidance1
Step 1: Understand the terms 'exergonic' and 'endergonic'. Exergonic reactions release energy and have a negative ΔG value, while endergonic reactions require energy input and have a positive ΔG value.
Step 2: Analyze the given reaction: L-Malate + NAD⁺ → Oxaloacetate + NADH + H⁺. The ΔG value is provided as +17 kcal/mol (+129.3 kJ/mol). Since the ΔG is positive, this reaction is endergonic, meaning it requires energy input to proceed.
Step 3: Identify whether the reaction produces a phosphate group. In this reaction, there is no mention of a phosphate group being produced or transferred. Therefore, this reaction does not directly produce a phosphate that later yields energy.
Step 4: Compare this reaction to other reactions in the catabolism of acetyl-CoA. Reactions that produce high-energy intermediates like ATP or GTP typically involve the transfer of phosphate groups, which is not the case here.
Step 5: Conclude that this reaction is endergonic due to its positive ΔG value and does not produce a phosphate group that later yields energy.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Exergonic and Endergonic Reactions
Exergonic reactions are those that release energy, typically characterized by a negative change in Gibbs free energy (∆G < 0). In contrast, endergonic reactions require an input of energy to proceed, indicated by a positive change in Gibbs free energy (∆G > 0). Understanding these concepts is crucial for analyzing metabolic pathways, as they dictate the direction and feasibility of biochemical reactions.
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Gibbs Free Energy (∆G)
Gibbs free energy is a thermodynamic potential that helps predict the direction of chemical reactions. It combines the system's enthalpy and entropy to determine whether a reaction can occur spontaneously. A negative ∆G indicates a spontaneous process, while a positive ∆G suggests that the reaction is non-spontaneous and requires energy input, which is essential for evaluating the reactions in the catabolism of acetyl-CoA.
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Phosphorylation and Energy Transfer
Phosphorylation is the addition of a phosphate group to a molecule, often resulting in energy transfer. In metabolic pathways, certain reactions produce high-energy phosphate compounds, which can later release energy by transferring their phosphate group to other molecules. This process is vital for cellular energy metabolism, as it allows the cell to harness energy from catabolic reactions for various biological functions.
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Related Practice
Textbook Question
What is the difference between catabolism and anabolism?
Textbook Question
What is the difference between digestion and metabolism?
Textbook Question
Why is ∆G a useful quantity for predicting the favorability of biochemical reactions?
Textbook Question
The electron-transport chain uses several different metal ions, especially iron, copper, zinc, and manganese. Why are metals used frequently in these two pathways? What can metals do better than organic biomolecules?
Textbook Question
The following reactions occur during the catabolism of glucose. Which are exergonic? Which is endergonic? Which proceeds farthest toward products at equilibrium?
b. Phosphoenol pyruvate + H2O → Pyruvate + Phosphate(Pi)
∆G = –14.8 kcal/mol (–61.9 kJ/mol)