Answer:
(i) Tissue P carries out cellular respiration by fermentation. In fermentation, glucose is partially broken down to produce energy without the presence of oxygen. This process occurs in the cytoplasm of the cells in tissue P. One common type of fermentation is called lactic acid fermentation. In this process, glucose is converted into lactic acid, producing a small amount of ATP (adenosine triphosphate) as a result. Lactic acid fermentation is commonly observed in muscle cells during intense exercise when oxygen supply is limited. This process helps generate energy to sustain muscle contractions when oxygen is not readily available.
(ii) Microorganism Q also carries out cellular respiration by fermentation. Similar to tissue P, microorganism Q can utilize fermentation as a way to obtain energy when oxygen is not present. Different types of microorganisms can undergo different types of fermentation. For example, yeast, a type of fungus, undergoes alcoholic fermentation. During this process, glucose is converted into ethanol and carbon dioxide, producing ATP as a byproduct. Alcoholic fermentation is used by yeast in bread-making and alcohol production. Other microorganisms may undergo different types of fermentation, depending on their metabolic capabilities.
(b) When an athlete is running, the body requires more energy to sustain the increased physical activity. Initially, the body relies on aerobic respiration, which requires oxygen and produces a significant amount of ATP. However, during intense exercise, the demand for energy exceeds the oxygen supply, leading to an oxygen debt.
The oxygen debt is built up because the body starts to rely on anaerobic respiration, which includes fermentation, to meet the energy demand. As a result, lactic acid fermentation occurs, converting glucose into lactic acid and producing ATP. This allows the muscles to continue contracting despite the insufficient oxygen supply.
After the athlete stops running, the body gradually settles the oxygen debt. The excess lactic acid produced during exercise needs to be cleared from the muscles. This process occurs during the recovery period, where the body continues to breathe in oxygen and remove the lactic acid. The oxygen is used to convert the accumulated lactic acid back into glucose through a process called the Cori cycle. This glucose can then be stored as glycogen in the liver and muscles or used as a fuel source for future energy needs.
In summary, an oxygen debt is built up when an athlete is running due to the reliance on anaerobic respiration and fermentation to generate energy. After the activity, the body settles the oxygen debt by removing lactic acid and replenishing oxygen levels through continued respiration.