How is energy produced in cells during anaerobic conditions?

Energy is produced in cells during anaerobic conditions through a process called anaerobic respiration or fermentation.

Anaerobic respiration, also known as fermentation, is a process that occurs in cells when oxygen is not available. This process allows cells to produce energy without the need for oxygen, which is crucial for survival in anaerobic conditions. The process is less efficient than aerobic respiration, which uses oxygen, but it allows cells to continue functioning when oxygen is scarce.

The process begins in the cytoplasm of the cell, where glucose is broken down into two molecules of pyruvate in a process called glycolysis. This process produces a small amount of ATP (adenosine triphosphate), which is the cell's main energy currency. In the absence of oxygen, the pyruvate is then converted into lactic acid in animal cells or ethanol and carbon dioxide in yeast and plant cells. This process does not produce any additional ATP, but it allows glycolysis to continue by recycling the NAD+ needed for this process.

In terms of energy yield, anaerobic respiration is less efficient than aerobic respiration. While aerobic respiration can produce up to 38 molecules of ATP from a single molecule of glucose, anaerobic respiration only produces 2 molecules of ATP. However, the ability to produce energy without oxygen is a crucial survival mechanism for cells in anaerobic conditions.

In summary, energy is produced in cells during anaerobic conditions through the process of anaerobic respiration or fermentation. This process involves the breakdown of glucose into pyruvate, which is then converted into lactic acid or ethanol and carbon dioxide, depending on the type of cell. This process allows cells to produce energy in the absence of oxygen, albeit at a lower efficiency than aerobic respiration.