Question
In eukaryotic cells, each stage of cellular metabolism generates a different net amount of ATP. Which stage directly generates the greatest number of ATP molecules per metabolized glucose molecule? electron transport chain and ATP synthase glycolysis fermentation citric acid cycle (Krebs cycle)
Answer
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Miranda
Master · Tutor for 5 years
Answer
To answer this question, let's break down each stage of cellular metabolism mentioned and how they contribute to ATP production. ATP, or adenosine triphosphate, is the energy currency of the cell, and different metabolic pathways contribute to its production in varying amounts.1. **Electron Transport Chain and ATP Synthase**: This is the final stage of aerobic respiration, where most ATP is produced. After glucose undergoes glycolysis and the citric acid cycle, the high-energy electrons from NADH and FADH2 are transferred through the electron transport chain in the mitochondria's inner membrane. This process creates a proton gradient, driving ATP synthase to synthesize ATP. It generates about 34 ATP molecules per glucose molecule.2. **Glycolysis**: This is the first step in both aerobic and anaerobic respiration, where one molecule of glucose is broken down into two molecules of pyruvate. This process takes place in the cytoplasm and nets 2 ATP molecules per glucose molecule.3. **Fermentation**: This anaerobic process allows cells to produce ATP without oxygen. Fermentation follows glycolysis if oxygen is not present, converting pyruvate into either lactate (lactic acid fermentation) or ethanol and CO2 (alcoholic fermentation), with a net gain of 2 ATP per glucose molecule.4. **Citric Acid Cycle (Krebs Cycle)**: This aerobic process takes place in the mitochondria and processes the products of glycolysis to produce NADH and FADH2, which are then used by the electron transport chain. It directly contributes a small amount of ATP (2 ATP per glucose molecule) and a greater amount indirectly through the electron transport chain.**Comparing these stages**, the **electron transport chain and ATP synthase** directly generate the greatest number of ATP molecules per metabolized glucose molecule, mainly because it is the stage where the energy from NADH and FADH2, produced by glycolysis and the citric acid cycle, is converted into a large amount of ATP.**Answer**: The stage that directly generates the greatest number of ATP molecules per metabolized glucose molecule is the **electron transport chain and ATP synthase**.