Respiration is an energy releasing reaction that occurs in living things. It can be anaerobic without the presence of oxygen or aerobic, with oxygen gas present. Anaerobic respiration can produce 2 ATP molecules. This is the "energy currency" a cell needs to live and carry out life functions. Glucose provides the stored energy that is acted upon by anaerobic bacteria and yeast and the end result is 2 ATP which provides enough energy from them to survive as well as waste products. This type of respiration is called fermentation. Aerobic respiration is a much more efficient process. Plants, animals, fungi and protists combine oxygen and glucose to release 36 ATP to be used as fuel and the wastes carbon dioxide and water vapor are also produced. All life requires energy to fuel the life activities needed to stay alive. The stored chemical energy is found in glucose, can be ultimately traced to the sunlight that plants need to produce glucose via photosythesis.