Question

………… is used for respiration in living organisms which reacts with foods and releases energy.

Answer 1

Respiration process takes place in living cells. Living organisms such as prokaryotes and Eukaryotes use respiration mechanisms for breakdown of food.In respiration process energy is obtained by breakdown of digested food.

Complete answer:
Respiration is a Fundamental metabolic process that takes place in the living cells of an organism, they produce energy by intake of oxygen into cells by eliminating waste products (carbon dioxide) from the human body. Most living organisms need oxygen to obtain energy from food. The Oxygen present in the cells reacts with glucose and releases energy in the form of ATP, this energy is used by living cells.
Respiration is of two types : Aerobic Respiration and Anaerobic respiration.
Aerobic respiration process takes place only in the presence of air. This process is by breakdown of food (glucose) into carbon dioxide and water. The energy release in the form ATP is used by the living organism. Most living organisms (Human, Animals, Insects) use aerobic respiration because they release more energy during the breakdown of glucose.

Anaerobic Respiration process takes place in absence of oxygen. This process takes place by breakdown of food ( glucose) into alcohol and carbon dioxide with release of energy. Certain organisms like Bacteria and yeast obtain energy through anaerobic respiration.

Thus, the correct answer is “Oxygen” is used for respiration in living organisms which reacts with foods and releases energy.

NOTE :
The organism which obtains energy with the use of oxygen is referred to as aerobes. The organism that obtains energy without the use of energy is referred to as Anaerobes.