The incomplete breakdown of glucose into alcohol, carbon dioxide and energy is referred to as

Step 1: Analyze the question The question describes glucose being broken down incompletely, producing alcohol (ethanol), carbon dioxide and a small amount of energy. We need the term for this process.

Step 2: Explain the concept Glucose can be broken down in two main ways:

• Aerobic respiration (oxygen present): glucose is completely broken down into carbon dioxide and water, releasing a large amount of energy. C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + energy (about 2870 kJ)

• Anaerobic respiration (no oxygen): glucose is only partly broken down. In yeast and some plant tissues, this gives ethanol and carbon dioxide with little energy. This is called fermentation. C₆H₁₂O₆ → 2C₂H₅OH + 2CO₂ + energy (about 210 kJ)

Step 3: Check each option

• A. Decay: breakdown of dead organic matter by bacteria and fungi, not specifically glucose to alcohol.
• B. Digestion: breakdown of large food molecules into small soluble ones by enzymes. No alcohol is produced.
• C. Fermentation: incomplete breakdown of glucose to alcohol, CO₂ and energy. ✔
• D. Oxidation: addition of oxygen or loss of electrons or hydrogen. Too general.
• E. Respiration: a broad term for energy release from food. Complete aerobic respiration yields CO₂ and water, not alcohol.

Step 4: Answer The correct answer is C. fermentation.

Exam tip: Remember the key phrase "yeast + no oxygen = alcohol + CO₂." If you see alcohol in a question about glucose breakdown, think fermentation. If you see lactic acid in muscles, that is anaerobic respiration in animals.