Photosynthesis
Photosynthesis
What is it?
Any organism that generates its own food through
biochemical processes is called an autotroph. A photoautotroph is any autotroph which produces its own food as well as other organic molecules through photosynthesis. Photosynthesis is the process by which organic compounds such as carbohydrates are synthesized using light energy from the sun. Photosynthetic organisms include plants, some protists, and some bacteria. By converting solar energy to chemical energy, photosynthetic organisms can transform simple inorganic materials from the atmosphere and/or the soil into complex organic molecules that are essential to sustaining life on earth. The overall chemical equation for photosynthesis is as follows:
6CO2 + 12H2O —> C6H12O6 + 6O2 + 6H2O
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As depicted by the equation, carbon dioxide and water molecules are harvested to produce glucose, oxygen, and water. The primary product of photosynthesis is glucose, but photosynthesis is also responsible, either directly or indirectly, for the production of all of the organic molecules essential to plant life.
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Why is Photosynthesis Important?
The sun is the primary source of energy which sustains life
on planet earth, but for it to be useful it must be converted to other forms. Photosynthesis does precisely that. As the predominant link between solar energy and living organisms, photosynthesis is arguably the most important organic process on earth. Directly or indirectly, nearly all biological needs are fulfilled in some way by photosynthesis. The energy humans and animals obtain by consuming food is derived from the byproducts of this process. The oxygen that breathes life into humans and animals alike is a product of photosynthesis. The energy produced as heat from burning firewood is contained in carbohydrates within the wood, which are also byproducts of the process. Similarly, the energy that fuels modern society which is stored in petroleum, natural gas, and coal indirectly comes from sunlight, and consequently photosynthesis.
Leaf Anatomy and Photosynthetic Processes
The structure of a leaf is specially suited to facilitate photosynthesis. Photosynthetic reactions are organized into two categories: light-dependent reactions and light-independent reactions (otherwise known as the Calvin Cycle). In eukaryotes, photosynthesis occurs in structures called chloroplasts, which are located in the leaves of plants and algae. Chloroplasts contain chlorophyll and other photosynthetic pigment molecules that absorb light from the sun. Light reactions are carried out on the thylakoid membrane of the chloroplasts, and where light energy from the sun is converted into ATP and NADPH. The Calvin Cycle takes place in the stroma of chloroplasts, where the ATP and NADPH produced by the light reactions is used to fix carbon dioxide into organic molecules. See the "Light-Dependent Reactions" and the "Calvin Cycle" tabs for more detailed descriptions of these processes.
