ATP

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=== In general  ===
 
=== In general  ===
  
ATP ([[Adenosine|adenosine&nbsp;triphosphate]]) is a high energy molecule that is [[Hydrolysed|hydrolysed]] to provide [energy] for many reactions within [[Cell|cells]]. ATP is mainly synthesised in the [[Mitochondria|mitochondria]]&nbsp;of a [[Cell|cell]], in a process called [[Oxidative phosphorylation|oxidative phosphorylation]], via&nbsp;[[Electron transfer chain|electron transfer chain]]&nbsp;(sometimes alternatively known as chemiosmosis).&nbsp;A small amount of ATP is synthesised in the [[Cytoplasm|cytoplasm]] during [[Glycolysis|glycolysis]], and during the [[Krebs cycle|Krebs cycle]] in the [[Mitochondria|Mitochondria]].&nbsp;&nbsp;ATP&nbsp;is a very important source of energy for many cellular functions,&nbsp;including in [[Muscle|muscle]] contraction, [[Active transport|active transport]] and [[Condensation Reaction|condensation reactions]]. The [[Molecular|molecular]] structure of ATP constists of three [[Phosphate|phosphate]] groups linked to an [[Adenosine|adenosine]]&nbsp;core. These [[Phosphate group|phosphate groups]] are linked in series by two [[Phosphoanhydride bond|phosphoanhydride bonds]]&nbsp;<ref>Molecular Biology of the Cell,5th Edition, 2008 Alberts et al., page 61</ref>.<br>
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ATP ([[Adenosine|adenosine&nbsp;triphosphate]]) is a high energy molecule that is [[Hydrolysed|hydrolysed]] to provide [energy] for many reactions within [[Cell|cells]]. ATP is mainly synthesised in the [[Mitochondria|mitochondria]]&nbsp;of a [[Cell|cell]], in a process called [[Oxidative phosphorylation|oxidative phosphorylation]], via&nbsp;[[Electron transfer chain|electron transfer chain]]&nbsp;(sometimes alternatively known as chemiosmosis).&nbsp;A small amount of ATP is synthesised in the [[Cytoplasm|cytoplasm]] during [[Glycolysis|glycolysis]], and during the [[Krebs cycle|Krebs cycle]] in the [[Mitochondria|Mitochondria]].&nbsp;&nbsp;ATP&nbsp;is a very important source of energy for many cellular functions,&nbsp;including in [[Muscle|muscle]] contraction, [[Active transport|active transport]] and [[Condensation Reaction|condensation reactions]]. The [[Molecular|molecular]] structure of ATP constists of three [[Phosphate|phosphate]] groups linked to an [[Adenosine|adenosine]]&nbsp;core. These [[Phosphate group|phosphate groups]] are linked in series by two [[Phosphoanhydride bond|phosphoanhydride bonds]]&nbsp;<ref>Molecular Biology of the Cell,5th Edition, 2008 Alberts et al., page 61</ref>.<br>  
  
 
=== Formation during aerobic respiration  ===
 
=== Formation during aerobic respiration  ===
  
The first stage of [[Respiration|respiration]] is [[Glycolysis|glycolysis]], where there is a net gain of two ATP molecules. At first,&nbsp;[[Glucose|Glucose]]&nbsp;is phosphorylated on addition of two phosphates, provided from the [[Hydrolysis|hydrolysis]] of 2ATP&nbsp;↔ 2ADP + 2Pi, creating two molecules of triose phophate. THis is then oxidised, losing one hyrogen per molecule of triose phosphate, forming two molecules of [[Pyruvate|pyruvate]]. During this step, for molecules of ATP are synthesised from 4ADP + 4Pi. This stage of respiration occurs in the cytoplasm, but the product, pyruvate, moves to the matrix of the [[Mitochondria|mitochondria]] where the next 3 stages occur.&nbsp;<br>  
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The first stage of [[Respiration|respiration]] is [[Glycolysis|glycolysis]], where there is a net gain of two ATP molecules. At first, [[Glucose|glucose]]&nbsp;is phosphorylated on addition of two phosphates, provided from the [[Hydrolysis|hydrolysis]] of 2ATP&nbsp;↔ 2ADP + 2Pi, creating two molecules of triose phophate. This is then oxidised, losing one hyrogen per molecule of triose phosphate, forming two molecules of [[Pyruvate|pyruvate]]. During this step, four molecules of ATP are synthesised from 4ADP + 4Pi. This stage of respiration occurs in the cytoplasm, but the product, pyruvate, moves to the [[Matrix|matrix]] of the [[Mitochondria|mitochondria]] where the next 3 stages occur.&nbsp;<br>  
  
The next stage of [[Aerobic respiration]]&nbsp;is the link reaction, however no ATP is prduced during this step.  
+
The next stage of [[Aerobic respiration|aerobic respiration]]&nbsp;is the link reaction, however no ATP is prduced during this step.  
  
 
The third stage, the [[Krebs cycle|Krebs cycle]], produces one molecule of ATP per cycle. Since this cycle happens once per [[Pyruvate|pyruvate]] molecule, it occurs twice per molecule of glucose and so a total of 2 ATP molecules are produced per glucose.  
 
The third stage, the [[Krebs cycle|Krebs cycle]], produces one molecule of ATP per cycle. Since this cycle happens once per [[Pyruvate|pyruvate]] molecule, it occurs twice per molecule of glucose and so a total of 2 ATP molecules are produced per glucose.  
  
The final stage of aerobic respiration, [[Oxidative phosphorylation|oxidative phosphorylation]], is where the vast amount of ATP is synthesised. Hydrogen atoms in the mitochondrial matrix, released from reduced [[FAD|FAD and]] reduced [[NAD|NAD]], split into [[Protons|protons]] (H+) and [[Electrons|electrons]] (e-). The [[Electrons|electrons move]] along the [[Electron transport chain|electron transport chain]], losing energy at each carrier. This energy is used to pump protons into the intermembrane space, forming and [[Electrochemical gradient|electrochemical grandient]]. The protons diffuse down this electrochemical gradient via [[ATP synthase|ATP synthase]], which drives the synthesis of ATP from ADP and Pi. This process is called [[Chemiosmotic hypothesis|chemiosmosis]]. Another 28 molecules of ATP are produced during oxidatitive phosphorylation, totalling to 32 molecules of ATP per molecule of Glucose&nbsp;<ref>Books, C. and Books, C (2009) A2-level Biology AQA Revision, United Kingdom: Coordination Group publications LTD. Pages 22-25</ref>.  
+
The final stage of aerobic respiration, [[Oxidative phosphorylation|oxidative phosphorylation]], is where the vast amount of ATP is synthesised. Hydrogen atoms in the mitochondrial matrix, released from reduced [[FAD|FAD and]] reduced [[NAD|NAD]], split into [[Protons|protons]] (H<sup>+</sup>) and [[Electrons|electrons]] (e<sup>-</sup>). The [[Electrons|electrons move]] along the [[Electron transport chain|electron transport chain]], losing energy at each carrier. This energy is used to pump protons into the intermembrane space, forming and [[Electrochemical gradient|electrochemical grandient]]. The protons diffuse down this electrochemical gradient via [[ATP synthase|ATP synthase]], which drives the synthesis of ATP from ADP and Pi. This process is called [[Chemiosmotic hypothesis|chemiosmosis]]. Another 28 molecules of ATP are produced during oxidatitive phosphorylation, totalling to 32 molecules of ATP per molecule of glucose&nbsp;<ref>Books, C. and Books, C (2009) A2-level Biology AQA Revision, United Kingdom: Coordination Group publications LTD. Pages 22-25</ref>.  
  
 
=== ATP Hydrolysis  ===
 
=== ATP Hydrolysis  ===
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=== What makes ATP an efficient energy source  ===
 
=== What makes ATP an efficient energy source  ===
  
ATP is the most common energy source in most cellular metabolism. However, some other cellular [[Metabolism|metabolism]] were not driven by ATP. Such an example of the other energy currency used in cellular metabolism is [[GTP|guanosine triphosphate]]&nbsp;(GTP), [[Uridine triphosphate|uridine triphosphate]]&nbsp;(UTP), and&nbsp;[[Cytidine triphosphate]] ([[Cytidine triphosphate|CTD]]). Nonetheless, ATP is the most efficient energy source used in cellular metabolism. The reasons that ATP is more reliable than the other nucleoside triphosphate in producing energy are:  
+
ATP is the most common energy source in most cellular metabolism. However, some other cellular [[Metabolism|metabolism]] were not driven by ATP. Such an example of the other energy currency used in cellular metabolism is [[GTP|guanosine triphosphate]]&nbsp;(GTP), [[Uridine triphosphate|uridine triphosphate]]&nbsp;(UTP), and&nbsp;[[Cytidine triphosphate|cytidine triphosphate]] ([[Cytidine triphosphate|CTD]]). Nonetheless, ATP is the most efficient energy source used in cellular metabolism. The reasons that ATP is more reliable than the other nucleoside triphosphate in producing energy are:  
  
 
*ATP have an unstable structure compared to ADP. Thus, ATP has a high phosphoryl-transfer potential (tendency to release phosphate to become ADP is high)&nbsp;<ref>Berg, J.M., Tymoczko, J.L., Stryer, L. and Gatto, G.J., 2010. Biochemistry. 7th ed. England: W.H. Freeman and Company.</ref>  
 
*ATP have an unstable structure compared to ADP. Thus, ATP has a high phosphoryl-transfer potential (tendency to release phosphate to become ADP is high)&nbsp;<ref>Berg, J.M., Tymoczko, J.L., Stryer, L. and Gatto, G.J., 2010. Biochemistry. 7th ed. England: W.H. Freeman and Company.</ref>  
*At neutral [[PH|pH]], triphosphate of ATP have a great repulsion between each other. This is because, at pH 7, all the [[Phosphate|phosphate]] of ATP carries a negative charge. The electrostatic repulsion causes the phosphate group to be easily released&nbsp;<ref>Berg, J.M., Tymoczko, J.L., Stryer, L. and Gatto, G.J., 2010. Biochemistry. 7th ed. England: W.H. Freeman and Company.</ref>.
+
*At neutral [[PH|pH]], triphosphate of ATP have a great repulsion between each other. This is because, at pH 7, all the [[Phosphate|phosphate]] of ATP carries a negative charge. The [[Electrostatic repulsion|electrostatic repulsion]] causes the phosphate group to be easily released&nbsp;<ref>Berg, J.M., Tymoczko, J.L., Stryer, L. and Gatto, G.J., 2010. Biochemistry. 7th ed. England: W.H. Freeman and Company.</ref>.
  
 
=== References  ===
 
=== References  ===
  
 
<references /><br>
 
<references /><br>

Revision as of 10:08, 24 November 2017

           Adenosine Triphosphate
Atp.gif
Adenine base (Red), Ribose (Pink), Phosphate (Blue) [1]

Contents

In general

ATP (adenosine triphosphate) is a high energy molecule that is hydrolysed to provide [energy] for many reactions within cells. ATP is mainly synthesised in the mitochondria of a cell, in a process called oxidative phosphorylation, via electron transfer chain (sometimes alternatively known as chemiosmosis). A small amount of ATP is synthesised in the cytoplasm during glycolysis, and during the Krebs cycle in the Mitochondria.  ATP is a very important source of energy for many cellular functions, including in muscle contraction, active transport and condensation reactions. The molecular structure of ATP constists of three phosphate groups linked to an adenosine core. These phosphate groups are linked in series by two phosphoanhydride bonds [2].

Formation during aerobic respiration

The first stage of respiration is glycolysis, where there is a net gain of two ATP molecules. At first, glucose is phosphorylated on addition of two phosphates, provided from the hydrolysis of 2ATP ↔ 2ADP + 2Pi, creating two molecules of triose phophate. This is then oxidised, losing one hyrogen per molecule of triose phosphate, forming two molecules of pyruvate. During this step, four molecules of ATP are synthesised from 4ADP + 4Pi. This stage of respiration occurs in the cytoplasm, but the product, pyruvate, moves to the matrix of the mitochondria where the next 3 stages occur. 

The next stage of aerobic respiration is the link reaction, however no ATP is prduced during this step.

The third stage, the Krebs cycle, produces one molecule of ATP per cycle. Since this cycle happens once per pyruvate molecule, it occurs twice per molecule of glucose and so a total of 2 ATP molecules are produced per glucose.

The final stage of aerobic respiration, oxidative phosphorylation, is where the vast amount of ATP is synthesised. Hydrogen atoms in the mitochondrial matrix, released from reduced FAD and reduced NAD, split into protons (H+) and electrons (e-). The electrons move along the electron transport chain, losing energy at each carrier. This energy is used to pump protons into the intermembrane space, forming and electrochemical grandient. The protons diffuse down this electrochemical gradient via ATP synthase, which drives the synthesis of ATP from ADP and Pi. This process is called chemiosmosis. Another 28 molecules of ATP are produced during oxidatitive phosphorylation, totalling to 32 molecules of ATP per molecule of glucose [3].

ATP Hydrolysis

Hydrolysing ATP to ADP (adenosine diphosphate) or further to AMP (adenosine monophosphate) releases a large amount of free energy, because the phosphoanhydride bonds in the molecule are broken [4]. ATP is, however, a very stable molecule and will only release its energy in the presence of ATPase.

ATP Cycle

ATP ↔ ADP +Pi

The formation of ATP requires an input of energy, therefore it must be coupled to energy-generating processes, such as photosynthesis or oxidation of food molecules. Hydrolysis of ATP releases a lot of free energy, therefore it must be coupled to energy-requiring processes such as muscle contraction and active transport.[5]

What makes ATP an efficient energy source

ATP is the most common energy source in most cellular metabolism. However, some other cellular metabolism were not driven by ATP. Such an example of the other energy currency used in cellular metabolism is guanosine triphosphate (GTP), uridine triphosphate (UTP), and cytidine triphosphate (CTD). Nonetheless, ATP is the most efficient energy source used in cellular metabolism. The reasons that ATP is more reliable than the other nucleoside triphosphate in producing energy are:

References

  1. http://www.chm.bris.ac.uk/motm/atp/atp_text.htm
  2. Molecular Biology of the Cell,5th Edition, 2008 Alberts et al., page 61
  3. Books, C. and Books, C (2009) A2-level Biology AQA Revision, United Kingdom: Coordination Group publications LTD. Pages 22-25
  4. Stryer et al. 2006, Biochemistry, 5th edition, W.H. Freeman and Company, New York.
  5. Lodish H, Berk A, Zipursky SL, et al. Molecular Cell Biology. 4th edition. New York: W. H. Freeman; 2000. Section 2.4, Biochemical Energetics. [Online} Available from: http://www.ncbi.nlm.nih.gov/books/NBK21737/ [Accessed:25/11/2014]
  6. Berg, J.M., Tymoczko, J.L., Stryer, L. and Gatto, G.J., 2010. Biochemistry. 7th ed. England: W.H. Freeman and Company.
  7. Berg, J.M., Tymoczko, J.L., Stryer, L. and Gatto, G.J., 2010. Biochemistry. 7th ed. England: W.H. Freeman and Company.

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