That's odd. Here it is copy and pasted. I'll make sure to lock the file following the rating. Use the above answer post for rating :)
All living organisms have a constant need to produce energy in order to power al the different forms of cell work. Cell work includes growth, respire, transport, and protein synthesis that aid in the metabolic function of an organism. Therefore, every organism has methods of obtaining, storing, and using energy. Organisms such as plants are considered autotrophs, as they can ‘self nourish’ or synthesize their own food. The process, by which autotrophs construct carbohydrates, or their food source, is through photosynthesis. Photosynthesis as defined by Campbell et al. 2008 is ‘ the conversion of light energy to chemical energy that is stored in sugars, or other organic compounds; occurs in plants, algae and certain prokaryotes.”
Photosynthesis can be summarized in reaction using the following chemical equation: 6 Carbon dioxide + 6 Water à glucose + 6 oxygen. The glucose produced in this process can be used immediately for cell respiration or converted into a storage form for future use. Plants store glucose as starch while animals store it as glycogen.
Respiration and photosynthesis are related. These two processes are in essence opposite reactions. Photosynthesis traps energy from sunlight in the chemical bonds of the glucose molecules. Cellular respiration then releases energy stored in the bonds and transfers it to a molecule of ATP. The process whereby carbon from the atmosphere is converted to glucose is called carbon fixation.
Photosynthesis consists of two different stages, the light-dependent reactions and the dark-dependent reactions. Light-dependent reactions occur in in the grana of a chloroplast. Grana are columns of stacked thylakoid discs that are distributed throughout the stroma, and the stroma is a semifluid internal substance similar to that of cytoplasm. Light reactions undergo several processes that are ordered as follows: photosystem II, electron transport chain, photosystem I, electron transport chain. During these photosynthesis processes hydrogen ions build up inside the discs, and as they pass across the disc membrane and back into the stroma, ATP is produced. Then, in the stroma the ATP is used to produce glucose. The photosynthetic pigments absorb light energy that is then used to split a water molecule. The electrons released from the slit water molecule are transferred to NADP+ forming NADPH and ATP. The oxygen left over from the split water molecule is released as a byproduct. NADPH and ATP pass to the next stage of photosynthesis, the dark reactions.
The dark reactions, also called the Calvin Cycle, occur in the stroma of the chloroplast. During this stage carbon dioxide is fixed into glucose molecules using the NADPH and ATP from the light-dependent reactions. This how the Calvin cycle begins, and is commonly referred as carbon fixation. While the light-dependent reactions received its names based on the fact that it requires light, the dark reactions received their name because this phase does not require light. Dark reactions will occur whenever there is carbon dioxide, NADPH, and ATP. This reaction doesn’t require dark conditions but can occur when light conditions do not exist.
At the on start of the Calvin cycle, carbon fixation occurs. One at a time, 3 molecules of carbon dioxide enter the system and react with the enzyme Rubisco. Three short lived intermediate molecules form 6 3-phosphoglycerates and at this point 6 ATPS inter the system and use these molecules to form 6 ADP. Next, a 1,3-biophosphoglycerates is formed and reduction occurs when NADPH is added to system, thereby releasing 6 NADP+ and 6P. Form this reaction glyceraldehyde 3-phosphaste is formed, which allows for 1 glucose molecule and other organic compounds to be formed and leave the system. After this, the carbon dioxide acceptor needs to be regenerated. The G3P receives 3 ATP and this forms 3 ADP, which leaves the system. After this the ribulose biphosphate is formed and the rubisco can now accept more carbon dioxide and allow the cycle to occur again.
There are some important differenced between light and dark reactions. Molecules in the thylakoid membranes carry out light reactions, where as dark reactions take place in the stroma. In light reactions, light energy is converted to chemical energy in the form of ATP and NADPH, where as dark reactions use AT and NADPH to convert carbon dioxide to the sugar G3P. Lastly, in light reaction water is split to release oxygen to the atmosphere, where as in Calvin reactions, ADP, inorganic phosphate, and NADP+ are returned to the light reactions.
Kingdom Plantae is perhaps one of the most diverse kingdoms in scientific nomenclature. Despite the diversity within, all plants utilize the processes of photosynthesis to gain nutrition in order to survive and reproduce. By plants being autotrophs and being able to create energy in a variety of conditions (i.e. light, temperature, soil acidity), they promote their own fitness. It could be argued that in some ways autotrophs are more fit than heterotrophs, which must rely on external sources for energy and ultimately survival. This is proven in numerous fields of science and especially those, which express how autotrophs, or primary producers, fuel an entire ecosystem. The ability for photoautotrophs to use both light and dark reactions to function properly is essential not only to the maintenance of their life, but to ours, too.
Campbell, Neil A., and Jane B. Reece. Biology, (2008). Vol. 98. No. 124. Benjamin Cumming's Publishing Company., 1984.
Farabee, M. J. "PHOTOSYNTHESIS." PHOTOSYNTHESIS. Maricopa University, 2007. Web. 14 Apr. 2013.
Mayer, G. (2006). Biological Principles. Cache House: Boca Raton, 167p.