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.
All living organisms need energy and matter from their environment. Matter is needed to make new cells (growth) and to create now organisms (reproduction), while energy is needed to drive all the chemical and physical processes of life, such as biosynthesis, active transport and movement.