Question

Consider the following chemical reactions which take place in different organisms/tissues under various conditions: \[\ce{Glucose ->[Respiration] Ethanol + Carbon dioxide + Energy}\] \[\ce{Glucose ->[Respiration] Carbon dioxide + Water +  Energy}\] \[\ce{Glucose ->[Respiration] Lactic acid + Energy}\]

1. Name one organism which respires according to equation (i) above.
2. Name one organism which respires according to equation (ii) above.
3. When and where does respiration represented by equation (iii) above take place?
4. Which equation/equations represent aerobic respiration?
5. Which equation/equations represent anaerobic respiration?
6. Which of the above reactions produces the maximum amount of energy?

Answer 1

1. Yeast shows anaerobic respiration (alcoholic fermentation), producing ethanol, carbon dioxide, and energy.
2. Humans (and most plants and animals) show aerobic respiration, producing carbon dioxide, water, and energy.
3. This occurs in the cytoplasm of skeletal muscle cells during vigorous physical exercise, when the oxygen supply is insufficient to meet the muscles’ energy requirements. It results in the formation of lactic acid and energy.
4. Aerobic respiration is equation (ii), because oxygen is used to completely oxidise glucose into carbon dioxide and water.
5. Anaerobic respiration is equations (i) and (iii), because they occur without sufficient oxygen.
6. Equation (ii) produces the maximum amount of energy because glucose is completely broken down during aerobic respiration.