there are two types of respiration. one is aerobic respiration and the other is anaerobic respiration. aerobic respiration happens in the presence of oxygen. oxygen breaks down food (glucose) to release high amounts of energy. anaerobic respiration happens in the absence of oxygen. during respiration in yeast and bacteria, oxygen is not involved in the oxidation of food. food (glucose) is broken down into ethyl alcohol and carbon dioxide this is called anaerobic respiration.