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.
Carbohydrates are the major source of energy for living organisms. Consider humans. We consume lots of carbohydrates everyday and these are in the complex form like oligosaccharides and disaccharides. They are broken down (in the digestive tract) into monosaccharides (like glucose).