laboratory execise 5 photosynthesis and cellularlaboratory exer.docxVIP

Laboratory Exercise #5Photosynthesis and Cellular RespirationI. IntroductionAll organisms, except for a few types of chemosynthetic bacteria, are ultimately dependent upon photosynthesis for their source of food. Photosynthesis is a photo-biochemical process that converts light energy into chemical energy by utilizing water and carbon dioxide to produce sugar, usually glucose, while releasing oxygen gas as a by-product. Light energy is trapped by the plant pigment molecules known as chlorophylls, xanthophylls, and carotenes. The sugar molecules made by photosynthesis may be used by the plant cells for energy production in the process of cellular respiration or may be converted to starch, cellulose, fats, amino acids, and other molecules, which may be used in function, structure, or stored for later use. These molecules of the plant cell may serve as food for other organisms such as animals or microbes.Several types of organisms carry out photosynthesis and are thus self-feeding, or autotrophic. These include cyanobacteria, protistans, and plants. Perhaps the most noticeable photosynthetic organisms are the seed plants, many of which we are dependent on for food, shelter, clothing, and medicines. Most seed plants carry out photosynthesis in specially adapted organs known as leaves. Photosynthesis is a very complex multi-step process that can be represented by the following equation:Light6 CO2 + 12 H2O → C6H12O6 + 6 O2 + 6 H2OEnergy is the ability to do work. Energy comes in many forms: heat, light, electrical, mechanical, chemical, and nuclear. All living organisms use energy for movement, for heat production, for active transport, for growth, and for reproduction. In fact, one of the most basic activities of a cell is the transformation of energy from less useful forms to more useful forms. During photosynthesis, energy from sunlight is stored in sugars. During cellular respiration, sugar molecules are oxidized (broken down) and energy is relea