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Adenosine Triphosphate, commonly known as ATP, is highly important in all biochemical processes. Without this energy rich compound, cellular metabolism would be so impossible. It is the principal energy source of the cell. The ATP supplies of the cell are usually produced in the mitochondria through the process of oxidative phosphorylation. Cellular activities that need energy spending fall into three common categories, and two rarer ones:
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Synthesis of New Chemical Compounds
The endoplasmic reticulum needs ATP to synthesize different important proteins like enzymes which facilitate fast chemical reactions. All cells employ ATP for this general purpose. Some cells, especially cells with high rate of secretion (e.g. salivary and digestive gland cells) and cells in the growth stage (e.g. developing germ cells), use up to 75% of the ATP they generate just to manufacture new chemical compounds (Lehninger 2005).
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The selective transport of nutrient and mineral molecules across the digestive tract wall requires ATP. Scientists think all cells employ ATP for at least some forms of transport. This can arrive at extremes in specialized transporters such as kidney tubules, which can use up as much as 80% of their ATP currency (Lehninger 2005) to operate their selective membrane transport mechanisms.
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ATP is needed for the contraction of skeletal and cardiac muscles. The heart must contract in order to pump blood toward the different parts of the body. The skeletal muscles should also contract in order for us to do different physical activities such as lifting an object. These activities entail great amount of ATP.
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ATP reacts with large carbon-nitrogen molecules (a luciferin) to produce photons in the visible range of wavelength. This use of ATP is somewhat rare on land, but is common in marine organisms, especially in the deep.
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ATP is generally used for the purposes of thermoregulation and other uses of high temperature. This occurs for useful purposes only in a few groups of organisms. Skeletal muscles and special heater tissues convert chemical-bond energy into heat.
As a consequence of cellular energy spending to support these different activities, large amount of ATP are manufactured. These energy-diminished ADP molecules enter the mitochondria for “recharging" and then the cycle back into the cytosol as energy-rich ATP molecules after participating oxidative phosphorylation. A single ADP/ATP molecule may transfer back and forth between the mitochondria and cytosol for this recharging/expenditure cycle thousands of times per day.
The high demands for ATP provide glycolysis alone an inadequate as well as ineffective supplier of power for most cells. If it were not for the mitochondria, which contain the metabolic machinery for oxidative phosphorylation, the energy capability of a cell would be very limited. However, glycolysis does provide at least some ATP under anaerobic conditions.
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Lehninger, Albert. 2005. Principles of Biochemistry. New York : W.H. Freeman