Textbook Question
Acetyl phosphate, whose structure is given here, is another compound with a relatively high free energy of hydrolysis.
Using structural formulas, write the equation for the hydrolysis of this phosphate.
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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 2a
The overall equation in this section,
shows the cycle between photosynthesis and oxidation. Pathways operating in opposite directions cannot be exergonic in both directions.
a. Which of the two pathways in this cycle is exergonic and which is endergonic?
Verified step by step guidance1
Understand the terms 'exergonic' and 'endergonic': Exergonic reactions release energy (ΔG < 0), while endergonic reactions require an input of energy (ΔG > 0). These terms are key to identifying the nature of the pathways in the cycle.
Identify the two pathways in the cycle: Photosynthesis and oxidation (cellular respiration). Photosynthesis involves the conversion of carbon dioxide and water into glucose and oxygen, while oxidation involves breaking down glucose into carbon dioxide and water.
Analyze photosynthesis: Photosynthesis requires energy input from sunlight to drive the reaction. Since it consumes energy, it is an endergonic process.
Analyze oxidation (cellular respiration): Oxidation releases energy stored in glucose molecules in the form of ATP. Since it releases energy, it is an exergonic process.
Conclude the analysis: Photosynthesis is the endergonic pathway in the cycle, and oxidation (cellular respiration) is the exergonic pathway. This aligns with the principle that pathways operating in opposite directions cannot both be exergonic.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Photosynthesis
Photosynthesis is the process by which green plants, algae, and some bacteria convert light energy into chemical energy, specifically glucose, using carbon dioxide and water. This process occurs in chloroplasts and involves two main stages: the light-dependent reactions and the Calvin cycle. Photosynthesis is endergonic, meaning it requires energy input, typically from sunlight, to drive the reaction.
Oxidation
Oxidation refers to the chemical process in which a substance loses electrons, often associated with the release of energy. In biological systems, oxidation is a key part of cellular respiration, where glucose is broken down to produce ATP, the energy currency of the cell. This process is exergonic, meaning it releases energy, which can be harnessed for various cellular activities.
Exergonic and Endergonic Reactions
Exergonic reactions are those that release energy, making them spontaneous and often occurring in the direction of decreasing free energy. In contrast, endergonic reactions require an input of energy to proceed, resulting in an increase in free energy. Understanding the distinction between these two types of reactions is crucial for analyzing metabolic pathways, such as the cycle between photosynthesis and oxidation.
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Textbook Question
A common metabolic strategy is the lack of reactivity—that is, the slowness to react—of compounds whose breakdown is exergonic. For example, hydrolysis of ATP to ADP or adenosine monophosphate (AMP) is exergonic but does not take place without an appropriate enzyme present. Why would the cell use this metabolic strategy?
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Textbook Question
One of the steps in lipid metabolism is the reaction of glycerol (1,2,3-propanetriol, HOCH2CH(OH)CH2OH, with ATP to yield glycerol 1-phosphate. Write the equation for this reaction using the curved arrow symbolism.
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