Textbook Question
Look at the eight steps of the citric acid cycle (Figure 21.8) and answer the following questions:
a. Which steps involve oxidation reactions?
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Ch.21 The Generation of Biochemical Energy
McMurry8th EditionFundamentals of GOBISBN: 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
Chapter 21, Problem 56
How many NADH and how many FADH2 molecules are formed in the citric acid cycle?
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 also produces electron carriers like NADH and FADH2, which are used in the electron transport chain to produce ATP.
Identify the key steps in the citric acid cycle where NADH is produced: NADH is formed during three specific reactions in the cycle. These occur during the oxidation of isocitrate to α-ketoglutarate, the oxidation of α-ketoglutarate to succinyl-CoA, and the oxidation of malate to oxaloacetate.
Identify the step in the citric acid cycle where FADH2 is produced: FADH2 is formed during the oxidation of succinate to fumarate, which is catalyzed by the enzyme succinate dehydrogenase.
Count the number of NADH molecules produced per turn of the cycle: Since there are three reactions that produce NADH, one turn of the citric acid cycle generates three NADH molecules.
Count the number of FADH2 molecules produced per turn of the cycle: Since there is one reaction that produces FADH2, one turn of the citric acid cycle generates one FADH2 molecule.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Citric Acid Cycle
The citric acid cycle, also known as the Krebs cycle, is a series of chemical reactions used by all aerobic organisms to generate energy. It occurs in the mitochondria and is a key component of cellular respiration, where acetyl-CoA is oxidized to produce energy carriers, including NADH and FADH2.
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Citric Acid Cycle Summary Concept 12
NADH and FADH2
NADH and FADH2 are electron carriers produced during the citric acid cycle. NADH is generated from the reduction of NAD+ during specific reactions, while FADH2 is produced from the reduction of FAD. Both molecules play a crucial role in the electron transport chain, where they help generate ATP.
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Energy Yield
The energy yield from the citric acid cycle is significant, as it produces three NADH and one FADH2 per turn of the cycle. Since each NADH can generate approximately 2.5 ATP and each FADH2 about 1.5 ATP during oxidative phosphorylation, understanding their production is essential for calculating the total energy output from glucose metabolism.
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Related Practice
Textbook Question
Look at the eight steps of the citric acid cycle (Figure 21.8) and answer the following questions:
b. Which steps involve decarboxylation (loss of CO2)?
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Textbook Question
Look at the eight steps of the citric acid cycle (Figure 21.8) and answer the following questions:
c. Which step or steps involve a hydration reaction?
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Textbook Question
Which reactions of the citric acid cycle transfer energy as FADH2?
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Textbook Question
Which reactions of the citric acid cycle transfer energy as NADH?
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Textbook Question
What are the two primary functions of the electron-transport chain?
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