Ch.18 Metabolic Pathways and ATP Production

Timberlake - Chemistry: An Introduction to General, Organic, and Biological Chemistry 13th Edition

Timberlake13th EditionChemistry: An Introduction to General, Organic, and Biological ChemistryISBN: 9780134421353Not the one you use?Change textbook

Timberlake 13th Edition

Ch.18 Metabolic Pathways and ATP Production

Problem 97d

Chapter 18, Problem 97d

Which of the following molecules will produce the most ATP per mole?
d. glucose or caprylic acid (C₈)

Verified step by step guidance

Step 1: Understand the context of ATP production. ATP (adenosine triphosphate) is produced during cellular respiration, which involves the breakdown of molecules like glucose and fatty acids. The amount of ATP generated depends on the number of carbon atoms and the energy yield from the molecule's oxidation.

Step 2: Compare the structures of glucose and caprylic acid (C₈). Glucose is a carbohydrate with six carbon atoms (C₆H₁₂O₆), while caprylic acid is a fatty acid with eight carbon atoms (C₈H₁₆O₂). Fatty acids generally produce more ATP per carbon atom than carbohydrates due to their higher energy density.

Step 3: Analyze the metabolic pathways. Glucose undergoes glycolysis, the citric acid cycle, and oxidative phosphorylation, yielding ATP. Caprylic acid undergoes beta-oxidation, the citric acid cycle, and oxidative phosphorylation, which typically produces more ATP per carbon atom than glucose due to the energy-rich nature of fatty acids.

Step 4: Consider the number of carbon atoms. Caprylic acid has more carbon atoms (8) compared to glucose (6), and each carbon atom contributes to ATP production during cellular respiration. This suggests caprylic acid may produce more ATP per mole.

Step 5: Conclude based on energy yield. Fatty acids like caprylic acid generally produce more ATP per mole than carbohydrates like glucose because of their higher energy density and longer carbon chains, which provide more opportunities for ATP generation during metabolism.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

ATP Yield from Different Molecules

Adenosine triphosphate (ATP) is the primary energy currency in cells. Different molecules yield varying amounts of ATP during cellular respiration. For instance, glucose typically produces about 30-32 ATP molecules per mole, while fatty acids like caprylic acid (C₈) can yield more ATP due to their longer carbon chains and higher energy content.

Cellular Respiration

Cellular respiration is the metabolic process by which cells convert nutrients into energy. It involves glycolysis, the citric acid cycle, and oxidative phosphorylation. Understanding this process is crucial for determining how different substrates, such as glucose and fatty acids, are metabolized to produce ATP.

Fatty Acid Oxidation

Fatty acid oxidation is the process by which fatty acids are broken down in the mitochondria to generate ATP. This process is more efficient than glucose metabolism in terms of ATP yield per carbon atom, especially for long-chain fatty acids. Caprylic acid, being an 8-carbon fatty acid, undergoes beta-oxidation, leading to a significant ATP production compared to glucose.

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