What Is ATP?

What is ATP? It is the activated carrier which gives organisms energy. How is it synthesized? Due to coupling of energetically favorable and unfavorable reactions we can live. How?

Activated carriers are a form of cellular currency. If a cell needs to have a reaction take place, however they do not have enough energy, they utilize an activated carrier. The most prevalent activated carrier in cells is adenosine 5'-triphosphate (ATP). Many different cellular metabolic processes have a net gain of ATP, such as: the citric acid cycle, and glycolysis. Although the production of ATP is an energetically unfavorable one, it is traditionally coupled to a necessary and favorable reaction, such as the above listed cellular metabolic ones.

The synthesis of ATP is a phosphorylation reaction in which a phosphate group (PO4) is added to adenosine 5'-diphosphate (ADP). It is important to note however, that the synthesis and use of ATP is a circular process. When ATP is needed in order to power an energetically unfavorable reaction, it delivers it's extra phosphate group, which is very energetic. Afterwards, it is once again ADP, and can be used as a substrate in cellular metabolic reactions.

When a reaction, such as a synthesis of two molecules, is necessary, ATP facilitates it. The hydrolysis of ATP provides energy which allows the typically energetically unfavorable reaction to proceed. The phosphates of ATP are linked by phosphoanhydride bonds. When an inorganic phosphate is needed as energy packet, the terminal phosphate is typically the one used.



How is ATP produced? ATP is produced by the breakdown of sugars and fats. However, the catch to the entire process is that in order to produce ATP, two molecules must be invested, or provided. In order to even commence glycolysis, two molecules of ATP must be supplied. Later on in the process, four molecules are created, thus having a net gain of two ATP.

It is important to note that in the citric acid cycle, ATP is not produced, however a close relative, GTP (guanosine triphosphate) is created. In the third stage of cellular metabolism, an ATP pump is used to transport substances throughout the cell.

There are many other activated carriers in organisms, such as: NADH, NADPH, FADH2, Acetyl CoA, Carboxylated biotin, S-Adenosylmethionine, and Uridine diphosphate glucose. The high energy groups which they carry are respectively: electrons, hydrogen, electrons, acetyl group, carboxyl group, methyl group, and glucose.

How exactly does a reaction use these activated carriers? Through coupling, as mentioned above, however how does a reaction become coupled to another? When a reaction has a negative delta G, or free energy, it is spontaneous, and does not need an activated carrier. However, when a reaction has a positive delta G, it needs the activated carriers which have thus far been named. In such a case, for example in ATP, the metamorphous of a phosphoanhydride bond into a phosphoester bond, which is by in itself a spontaneous reaction, donates it's energy to the positive delta G reaction.

However, it is crucial to understand that the ATP is not simply being charitable. It is imperative that the ATP be converted back into it's ADP form in order to continue allowing cellular metabolic processes. This is the theory behind activated carriers, specifically ATP and ADP.

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