Acid anhydride bonds, which are present in high energy compounds, are created by the condensation of 2 acidic groups or similar compounds. Because free energy is released when these bonds are hydrolysed, they are referred to as high energy bonds. Here, let’s learn more about the high energy compounds and ATP which is the most significant high energy compound in living cells.
Table of Contents
- High Energy Compounds
- Types of High Energy Compounds
- ATP – Cell’s Energy Currency
- Frequently Asked Questions
High Energy Compounds
What are high energy compounds?
High energy compounds are also called energy-rich compounds. Compounds present in the biological system that when hydrolysed, produce free energy that is greater or equal to that of ATP (â–³G is -7.3 kcal/mol) are termed high energy compounds.
Low-energy compounds have an energy yield of less than -7.3 kcal/mol. High-energy bonds are found in the majority of high-energy compounds that produce energy upon hydrolysis. Most of the high energy compounds contain phosphate groups and thus they are also termed high-energy phosphates. These high energy compounds are mainly classified into five groups:
- Pyrophosphates
- Acyl phosphate
- Enol phosphate
- Thiol phosphate
- Phosphagens or guanido phosphates
Types of High Energy Compounds
The energy released during catabolism is captured in the form of a group of compounds called high energy phosphates. There are also high energy compounds belonging to the sulphur group like acetyl CoA, succinyl CoA and fatty acyl CoA.
High Energy Compounds Examples
Pyrophosphates
Pyrophosphate energy bonds are nothing but acid anhydride bonds. Condensation of acid groups (primarily phosphoric acid) or their derivatives results in the formation of these bonds. ATP (â–³G = -7.3 kcal/mol) is an example of a pyrophosphate. It has two phosphoanhydride diphosphate bonds.
Acyl phosphates
The reaction between the carboxylic acid group and the phosphate group forms a high energy bond in this compound.1,3-bisphosphoglycerate (â–³G = -11.8 kcal/mol) is an example of acyl phosphate.
Enol phosphates
The enol phosphate bond is present here. It is formed when a phosphate group binds to a hydroxyl group that is bound to a double-bonded carbon atom. As an example, consider phosphoenolpyruvate (â–³G = -14.8 kcal/mol).
Thiol phosphates
There is no high energy phosphate bond here. Instead, a high energy thioester bond is found here. Thioester bonds are formed by the reaction of thiol and carboxylic acid groups. Acetyl CoA (â–³G = -7.7 kcal/mol) is an example.
Phosphagens
Guanidine phosphate bonds are present in phosphagens or guanido phosphates. The phosphate group is attached to the guanidine group to form it. Phosphocreatine (â–³G = -10.3 kcal/mol) is the most important compound with this type of bond.
Also Check: Life Processes
ATP – Cell’s Energy Currency
The majority of ATP is produced in the mitochondrial matrix during cellular respiration. Thus mitochondria are termed the powerhouse of the cell. ATP is a nucleotide made up of the molecule adenosine and three phosphate groups. It is water soluble and contains a lot of high energy due to the presence of 2 phosphoanhydride bonds connecting the 3 phosphate groups. As a significant amount of energy is released when they are broken, and they are referred to as high energy bonds. The available energy is stored in the phosphate bonds and is released when they are split into molecules. This is accomplished by the addition of a water molecule (hydrolysis). When the outer phosphate group of ATP is removed to yield energy, ATP is converted into ADP, which is the form of the nucleotide with only two phosphates.
Hydrolysis of ATP (exergonic)
ATP + H2O → ADP + Pi
Dehydration of ADP (endergonic)
ADP + Pi → ATP + H2O
Hydrolysis of ATP is associated with the release of large amounts of energy (7.3 kcal/mol) which is used for various processes like active transport, muscle contraction, etc.
The hydrolysis of ATP to AMP releases -10.9 kcal/mol of energy
ATP + H2O → AMP + PPi
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