Which of the following is the most efficient and abundant means of ATP production in eukaryotic cells?

• A. Substrate-level phosphorylation in the citric acid cycle
• B. Oxidative phosphorylation
• C. Fermentation
• D. Glycolysis

Answer: (B)

Verified step by step guidance

1. Understand the role of ATP in cellular processes: ATP (adenosine triphosphate) is the primary energy currency of the cell, and its production is essential for powering various biological functions.
2. Review the processes listed in the question: Substrate-level phosphorylation, oxidative phosphorylation, fermentation, and glycolysis. Each of these contributes to ATP production but varies in efficiency and abundance.
3. Explain oxidative phosphorylation: This process occurs in the mitochondria and involves the electron transport chain and chemiosmosis. Electrons are transferred through protein complexes, creating a proton gradient across the inner mitochondrial membrane. The enzyme ATP synthase uses this gradient to produce ATP. This is the most efficient method of ATP production in eukaryotic cells.
4. Compare oxidative phosphorylation to other methods: Substrate-level phosphorylation produces ATP directly during specific steps of glycolysis and the citric acid cycle but is less efficient. Fermentation is an anaerobic process that generates ATP without oxygen but produces far less ATP. Glycolysis is the initial step of glucose metabolism and generates ATP, but it is not as efficient as oxidative phosphorylation.
5. Conclude why oxidative phosphorylation is the correct answer: It is the most efficient and abundant means of ATP production in eukaryotic cells because it generates the majority of ATP during cellular respiration, utilizing oxygen and the electron transport chain.