Why can't anaerobic respiration sustain high-energy activities for long?

Anaerobic respiration cannot sustain high-energy activities for long because it produces less ATP and results in lactic acid build-up.

Anaerobic respiration, also known as fermentation, is a process that occurs in the absence of oxygen. It is a crucial survival mechanism for many organisms, allowing them to generate energy when oxygen is scarce. However, it is not as efficient as aerobic respiration in terms of ATP (adenosine triphosphate) production, the molecule that provides energy for most cellular functions.

In aerobic respiration, one glucose molecule can produce up to 38 molecules of ATP. In contrast, anaerobic respiration only produces 2 ATP molecules per glucose molecule. This means that anaerobic respiration provides less energy for the same amount of glucose, making it less efficient for sustaining high-energy activities over a long period.

Moreover, anaerobic respiration in humans results in the production of lactic acid. This is a by-product that can build up in the muscles during intense exercise, causing discomfort and fatigue. The accumulation of lactic acid can lower the pH in the cells, inhibiting enzyme activity and thus slowing down the metabolic processes. This is why after a short burst of intense activity, such as sprinting, your muscles start to feel tired and you need to slow down or stop to allow your body to remove the lactic acid and switch back to aerobic respiration.

In conclusion, while anaerobic respiration is a useful mechanism for short bursts of high-intensity activity, it cannot sustain such activities for a long time due to its lower ATP yield and the build-up of lactic acid.