Explain the stages of respiration in detail.

Respiration is a multi-step process through which energy is released from glucose. It occurs in three main stages, each with specific functions.

The first stage is glycolysis, which takes place in the cytoplasm. In this step, one molecule of glucose is broken down into two molecules of pyruvate. A small amount of energy (ATP) is produced, and this stage does not require oxygen.

The second stage is the Krebs cycle (also called the citric acid cycle), which occurs in the mitochondria. Pyruvate is further broken down, releasing carbon dioxide and generating energy-rich molecules such as NADH and FADH₂.

The third stage is the electron transport chain, which also occurs in the mitochondria. In this stage, electrons from NADH and FADH₂ are transferred through a series of reactions. Oxygen is used to produce a large amount of ATP, and water is formed as a by-product.

These stages together ensure the complete breakdown of glucose and efficient release of energy required for cellular activities.