Cold sores - painful sores on the lips and around the mouth, caused by a virus. Canker sores - painful sores in the mouth, caused by bacteria or viruses. Thrush - a yeast infection that causes white patches in your mouth. Leukoplakia - white patches of excess cell growth on the cheeks, gums or tongue, common in smokers.
Metabolism is a combination of chemical reactions that are spontaneous and release energy and chemical reactions that are non-spontaneous and require energy in order to proceed. Living organisms must take in energy via food, nutrients, or sunlight in order to carry out cellular processes.
Living organisms are able to exist because of a continual input of energy. Part of this energy is used to carry out essential functions- such as maintenance, growth and reproduction- and the remainder is lost in the form of heat. 2. The primary source of energy for most living organisms is the sun.