What is the importance of oxygen for living beings?

Oxygen is vital because most living beings use it to release energy from food, keep cells alive, and support life processes. In humans, animals, many plants, and most microbes, oxygen is used in aerobic respiration. This process happens in mitochondria and turns glucose and other nutrients into ATP (usable energy), with carbon dioxide and water as products. Without enough oxygen, cells cannot make enough energy, organs fail, and life stops.

Why oxygen matters (core points)

• Energy production: final electron acceptor in the electron transport chain to make ATP.
• Brain and heart function: very oxygen-sensitive; minutes without oxygen cause serious damage.
• Immune defense: white blood cells use oxygen to make reactive oxygen species to kill germs.
• Metabolism of nutrients: supports oxidation of fats, proteins, and carbohydrates.
• Plant life: plants also respire; in daylight, photosynthesis produces oxygen; at night, they still need oxygen for respiration.
• Ozone & atmosphere: oxygen in the air (~21%) supports life; ozone (O₃) absorbs harmful UV rays.
• Water and aquatic life: dissolved oxygen in water is essential for fish and other aquatic organisms.
• Medical uses: oxygen therapy helps in breathing problems, anesthesia, and emergency care.

Balanced cycle in nature

Photosynthesis by green plants and algae uses carbon dioxide and gives out oxygen, while animals and many microbes take oxygen and give out carbon dioxide. This oxygen–carbon dioxide cycle keeps atmospheric gases in balance.