Chapter: Life Processes in Living Organisms Part 1· Science & Technology Part 2
Answer: Respiration (cellular respiration) is the process in which food, mainly glucose, is oxidised inside the cells to release energy. This energy is stored in the form of ATP and is used for all the activities of the body.
Respiration is of two types:
- Aerobic respiration happens in the presence of oxygen. Glucose is completely oxidised to carbon dioxide and water. It takes place in three stages: glycolysis (in the cytoplasm), Krebs cycle and electron transfer chain (both in the mitochondria). One glucose molecule gives 38 ATP molecules.
\(\mathrm{C_6H_{12}O_6 + 6O_2 \rightarrow 6CO_2 + 6H_2O + energy\ (38\ ATP)}\) - Anaerobic respiration happens without oxygen. Glucose is only partly oxidised, so much less energy is released. For example, yeast makes ethanol and carbon dioxide (fermentation), and our muscle cells make lactic acid during heavy exercise.
Remember: breathing is only taking in oxygen and giving out carbon dioxide (a physical process). Respiration is the chemical process of oxidising food inside cells to get energy.
More on this chapter: aerobic vs anaerobic respiration, glycolysis explained, Krebs cycle with reaction, and all questions of Life Processes in Living Organisms Part 1.