Chapter 5 · Question 11
What are the different ways in which glucose is oxidized to provide energy in various organisms?
Answer
Direct Answer
Glucose is oxidised in three ways: aerobic respiration (with O2, producing CO2 + H2O + 38 ATP), anaerobic respiration (without O2, producing ethanol + CO2 + 2 ATP in yeast, or lactic acid + 2 ATP in muscle cells).
Simple Explanation
Glucose can be broken down in three ways: 1. With oxygen — this gives the most energy. 2. Without oxygen in yeast — this makes alcohol. 3. Without oxygen in our muscles — this makes lactic acid (causing cramps).
Exam-Ready Structure
Glucose (a six-carbon molecule) is broken down to release energy through three different pathways: 1. Aerobic respiration — In the presence of oxygen, glucose is completely oxidized to carbon dioxide and water, releasing a large amount of energy (38 ATP molecules per glucose molecule). This occurs in mitochondria. 2. Anaerobic respiration in yeast — In the absence of oxygen, glucose is converted to ethanol and carbon dioxide, releasing only 2 ATP per glucose molecule (fermentation). 3. Anaerobic respiration in muscle cells — During heavy exercise when oxygen supply is insufficient, glucose is converted to lactic acid, releasing only 2 ATP per glucose molecule. The accumulation of lactic acid causes muscle cramps.
Key Points
- Aerobic: glucose → CO2 + H2O + 38 ATP (in mitochondria)
- Anaerobic (yeast): glucose → ethanol + CO2 + 2 ATP
- Anaerobic (muscles): glucose → lactic acid + 2 ATP
- Aerobic respiration releases far more energy than anaerobic
Common Mistakes
- Saying anaerobic respiration produces the same energy as aerobic
- Confusing the end products of yeast fermentation and muscle respiration
Answer Sources
- Aerobic and anaerobic breakdown of glucosetextbook section | Science | Life Processes | Respiration pathways | Pages 10-11