Textbook Question
Each of these reactions is involved in one of the four stages of metabolism shown in Figure 21.4. Identify the stage in which each reaction occurs.
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b. Oxidation of NADH coupled with synthesis of ATP
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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 15
Which of the reactants in the citric acid cycle have two chiral carbon atoms?
Verified step by step guidance1
Understand the citric acid cycle: The citric acid cycle (also known as the Krebs cycle or TCA cycle) is a series of chemical reactions used by aerobic organisms to generate energy through the oxidation of acetyl-CoA. It involves several intermediates, some of which are chiral molecules.
Review the concept of chirality: A chiral carbon atom is a carbon atom that is bonded to four different groups. Molecules with chiral carbons can exist as non-superimposable mirror images (enantiomers).
Identify the intermediates in the citric acid cycle: The main intermediates include citrate, isocitrate, α-ketoglutarate, succinyl-CoA, succinate, fumarate, malate, and oxaloacetate. Not all of these intermediates are chiral.
Determine which intermediates have two chiral carbons: Analyze the molecular structure of each intermediate. For example, isocitrate has two chiral carbons because it contains two carbon atoms each bonded to four different groups.
Conclude that isocitrate is the reactant in the citric acid cycle with two chiral carbon atoms. Other intermediates may have one or no chiral carbons, but isocitrate specifically has two.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Chirality
Chirality refers to the geometric property of a molecule having a non-superimposable mirror image, much like left and right hands. A chiral carbon atom is one that is attached to four different substituents, leading to two distinct configurations, known as enantiomers. Understanding chirality is essential in biochemistry, as it can influence the behavior and interaction of molecules in biological systems.
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1:39
Chirality Example 1
Citric Acid Cycle
The citric acid cycle, also known as the Krebs cycle, is a key metabolic pathway that occurs in the mitochondria of cells. It plays a crucial role in cellular respiration by oxidizing acetyl-CoA to produce energy in the form of ATP, as well as electron carriers like NADH and FADH2. The cycle involves a series of enzymatic reactions, and understanding its components is vital for identifying reactants with specific structural features, such as chirality.
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2:31Citric Acid Cycle Summary Concept 12
Reactants in the Citric Acid Cycle
The reactants in the citric acid cycle include acetyl-CoA, oxaloacetate, and various intermediates such as citrate, isocitrate, and alpha-ketoglutarate. Each of these compounds plays a specific role in the cycle, and some contain chiral centers. Identifying which of these reactants have two chiral carbon atoms requires knowledge of their molecular structures and the ability to recognize chiral centers within them.
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2:31Citric Acid Cycle Summary Concept 12
Related Practice
Textbook Question
Why, do you suppose, the coenzyme for the reaction in the citric acid cycle that is catalyzed by succinate dehydrogenase is FAD and not NAD+?
Textbook Question
Look ahead to Figure 21.8 for the citric acid cycle.
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b. What class of enzymes carry out these reactions?
Textbook Question
The reduced coenzymes NADH and FADH2 are oxidized in the ETS. What is the final electron acceptor of the ETS? What is the function of the H+ ion in ATP synthesis?
Textbook Question
Identify the participants in the citric acid cycle that contain alcohol groups. Identify these groups as primary, secondary, or tertiary alcohols.
Textbook Question
Each of these reactions is involved in one of the four stages of metabolism shown in Figure 21.4. Identify the stage in which each reaction occurs.
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a. Hydrolysis of starch to produce glucose
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