Adenosine Triphosphate (ATP): Functions and Structure of ATP Molecule

Adenosine triphosphate, or ATP, is the chemical in which the bond energy of living systems resides. It is a kind of organic compound that provides energy required to run biochemical processes in living cells. This compound is found in all living systems and all living forms. ATP captures the chemical energy derived from digested food molecules and releases it for different biochemical processes in the body.

Read Also: Difference Between Catabolism and Anabolism

Key Words: Adenosine Triphosphate, ATP, ADP, Energy, Glucose, Cells, Phosphate, 

What is Adenosine Triphosphate?

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All living things on this earth require energy for the proper functioning of cells, tissues and organs and for driving the biochemical processes. Adenosine triphosphate is the compound which breaks down the chemical energy captured from digested food. 

This captured energy is used by the cell when the released phosphate binds itself to another molecule and activates it. For this reason, ATP is called the energy currency of the cell. During metabolic processes, ATP converts either to adenosine diphosphate (ADP) or adenosine monophosphate (AMP).

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Properties of Adenosine Triphosphate

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The properties of Adenosine Triphosphate (ATP) have been tabulated below:

Read Also: Discovery of Cells

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Structure of Adenosine Triphosphate

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ATP is a nucleotide that consists of three main structures:

• Adenine, which is the nitrogenous base
• Sugar ribose
• A chain of three phosphate groups tied to ribose
• The actual power source is the phosphate tail of ATP which is tapped by the cell.
• Energy captured is stored in the bonds between the phosphates and is released when they break (which occurs through hydrolysis).
• Adenine of the ATP is connected by the 9-nitrogen atom to the 1’ carbon of sugar ribose.
• The triphosphate group (comprising three phosphates) is connected to the 5th carbon of ribose.
• These three phosphate groups (called alpha, beta, gamma) play an important role in the release of energy.
• These groups are linked to each other by two high energy bonds called phosphoanhydride bonds.

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How is Adenosine Triphosphate Synthesized?

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Three steps are involved in the synthesis of ATP, which are discussed below briefly:

Glycolysis

This is a catabolic pathway since it constitutes degradation. Glucose is catabolized (degraded) to 3-carbon pyruvate molecules in this process. When the phosphorylation of glucose takes place, glucose is trapped. 

After the conversion of glucose into pyruvate, pyruvate molecules are then converted to lactate. 

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Citric Acid Cycle

In this phase, the triose which is derived from glycolysis is converted to 3 molecules of carbon dioxide. This provides energy for the respiratory chain in the form of electrons. 

Respiratory Chain

In this process, electrons are transported in mitochondria, chloroplasts, and the plasma membrane of the cells.

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Functions of Adenosine Triphosphate

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Functions of Adenosine Triphosphate (ATP) have been elaborated below:

Providing Energy

ATP is made up of three phosphate groups. When the bonds between these three groups break, a great amount of energy is released, which is enough to trigger a variety of cellular responses and mechanisms. 

The bond between the beta-gamma phosphate groups is broken to create adenosine diphosphate, along with a phosphate molecule. ATP is made when ADP combines with the free phosphate molecule. Energy is released when the bonds between the triphosphate groups break. This energy is used to run a number of vital biochemical processes taking place in our body like metabolism, responsiveness, reproduction, movements, etc.

ATP+H₂0 → ADP +Pi + Energy

ATP+H₂0 → AMP +PPi + Energy

DNA and RNA Synthesis

ATP plays an important role in the synthesis of RNA, by being one of the four monomers required for its production. ATP is also vital for DNA formation as ATP is first converted to deoxyribonucleotide before becoming DNA.

Synthesis of Macromolecules

ATP has a vital role in the synthesis of macromolecules that cells require for their survival. Apart from this, ATP aids various cellular functions including transportation of inter-cellular molecules across the membrane of the cells.

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Role of Adenosine Triphosphate in Metabolism

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Metabolism is an umbrella term used for all the chemical processes taking place inside the body. Cells require energy for these processes but this energy cannot be stored in its free form as it would be detrimental to the cell (due to the risk of elevated temperatures). 

Cells store energy in the form of the molecule ATP. Energy is released when the gamma phosphate group is removed from ATP. The molecule ATP is used to transport chemical energy in many processes associated with metabolism, such as:

• Aerobic Respiration
• Cellular Division
• Fermentation
• Protein Synthesis
• Motility

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Role of Adenosine Triphosphate in Medicine

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ATP is essential component of medicine. It is involved in following;

• ATP is used increase physical energy.
• Adenosine is used to treat surgical pain, nerve pain, pulmonary hypertension and irregular heartbeat.
• It is also administered for controlling blood pressure during anesthesia.
• To treat nerve pain, certain doctors administer adenosine into the space around the spinal cord.
• Adenosine phosphate is also given by injection into the muscle to treat:
• Varicose veins
• Pain and swollen tendons
• Itchiness
• Multiple sclerosis
• Herpes
• Genital Herpes
• Cold sores
• Poor blood circulation

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Things to Remember

• ATP is the energy currency of the cell.
• Its basic structure includes adenine, sugar ribose and triphosphate groups
• Energy is released when the terminal phosphate of ATP is removed.
• Synthesis of ATP is a three-step process and involves glycolysis, citric acid cycle and oxidative phosphorylation.
• ATP also plays a great role in medicine.

Read More: Difference Between Gram-Positive and Gram-Negative