What is photosynthesis?
Photosynthesis is the process by which plants, some bacteria, and some protistans use the energy from sunlight to produce sugar, which cellular respiration converts into ATP, the “fuel” used by all living things. The conversion of unusable sunlight energy into usable chemical energy, is associated with the actions of the green pigment chlorophyll. Most of the time, the photosynthetic process uses water and releases the oxygen that we absolutely must have to stay alive. Oh yes, we need the food as well!
Photosynthesis is a technique for converting sunlight into energy that has been utilized by certain organisms for around 3.4 billion years. The basic formula involves a conversion of carbon dioxide and water into glucose and oxygen, aided by light-dependent reactions. Photosynthesis emerged quickly after the emergence of life itself, thought to have occurred 3.5 billion years ago, after the Earth’s crust cooled. The first photosynthetic organisms were the ancestors of modern-day cyanobacteria. Photosynthesis takes place inside chloroplasts, special organelles located in the cells of plants and other photosynthesizing organisms. Choloroplasts are green because they utilize the pigment chlorophyll. The primary sun-absorbing organs of plants are the leaves. Although chloroplasts are located in cells throughout a plant, chloroplast density is by far the highest on the leaves, where between 450,000 and 800,000 chloroplasts can be found in every square millimeter.
Photosynthesis is arguably the most important biological process on earth. By liberating oxygen and consuming carbon dioxide, it has transformed the world into the hospitable environment we know today. Directly or indirectly, photosynthesis fills all of our food requirements and many of our needs for fiber and building materials. The energy stored in petroleum, natural gas and coal all came from the sun via photosynthesis, as does the energy in firewood, which is a major fuel in many parts of the world. This being the case, scientific research into photosynthesis is vitally important. If we can understand and control the intricacies of the photosynthetic process, we can learn how to increase crop yields of food, fiber, wood, and fuel, and how to better use our lands. The energy-harvesting secrets of plants can be adapted to man-made systems which provide new, efficient ways to collect and use solar energy. These same natural “technologies” can help point the way to the design of new, f
by Govindjee and Rajni Govindjee Photosynthesis converts massive amount of Sunlight into electrical and then chemical energy. The input is carbon dioxide (CO2), water (H2O), minerals and light, and the output is carbohydrates (food) that we need for our nourishment, and oxygen that we need to breathe [Ref. 1] This oxygenic photosynthesis occurs in higher plants (e.g., rice, maize, wheat, mosses, ferns, forest trees, shrubs, etc); in green, red, brown and yellow algae, and even blue-green cyanobacteria. There are photosynthetic bacteria (e.g., purple and green bacteria; and heliobacteria) that can produce carbohydrate (food), but no oxygen. They are called anoxygenic photosynthesizers. Instead of the all-abundant water, they use H2S or even organic matter. Oxygenic photosynthesizers use the green pigment Chlorophyll a, located in protein complexes in photosynthetic membranes, to run the photochemistry of the process, whereas the anoxygenic photosynthesizers use Bacteriochlorophyll inste
