ATP: Structure and its Functions

ATP or adenosine triphosphate is a nucleotide that provides energy that every cell in our body requires to perform various functions. Adenosine triphosphate is synthesized by the process known as photophosphorylation, cellular respiration, and fermentation. ATP is also known as energy currency as it gives energy to cells to perform various biological processes. ATP helps in the transfer and utilization of energy to perform functions like active transportation.

The function of ATP is to give energy for the functioning of cell signaling, cellular respiration, transportation, etc. In this article, we will discuss about Structure of ATP, its Function, importance, chemical properties, and its synthesis.

What is ATP-Adenosine Triphosphate?

ATP is the energy currency molecule that provides energy to the cells to perform various biological functions. ATP is composed of adenine nucleotide, ribose sugar, and triphosphate group. The phospho-anhydride bond in the phosphate group provides a high energy bond to hold molecules together thus making it energy currency. The breakdown of phosphate bonds in ATP releases a high amount of energy to perform biological functions.

After break down the ATP is broken down into Adenosine Diphosphate (ADP). This energy transfer is crucial for various biological processes, such as muscle contraction, active transport across cell membranes, and synthesis of macromolecules. The cyclic process between ATP and ADP allows cells to efficiently manage and utilize energy for their diverse functions.

Structure of ATP

1. ATP is composed of adenine which is linked to the 9^th nitrogen atom and forms the bond between the 1^st carbon atom of ribose sugar.
2. Ribose sugar is attached to the triphosphate group at the 5^th carbon atom.
3. Adenine and ribose sugar do not undergo any alteration while the phosphate group might get converted to diphosphate or monophosphate, which leads to the formation of ADP and AMP derivatives, respectively.
4. In ATP there is a phosphoryl group present which are designated as alpha, beta, and gamma (terminal phosphate).
5. The two phosphoanhydride bonds that bind the three phosphate groups together allow it to be soluble in water and have a large energy content.

Importance of ATP in Metabolism

ATP act as a crucial molecule in biological process and its importance are listed below:

1. Energy Source: ATP also called “energy currency” of cells as it acts as an energy storage house of cells. It is involved in so many cellular activities to provide energy such as transporation of molecules.
2. Cellular work: ATP aids in muscle contraction and movements of cells.
3. Synthesis: It is involved in various biological processes such as the synthesis of molecules. ATP also help in the breakdown of complex molecules into simpler molecules for example carbohydrate metabolism.
4. Transportation: Active transportation of molecules across the cell membrane is facilitated by ATP.
5. Activation of enzymes: There are several enzymes which require ATP for activation by transferring of phosphate group. This is known as phosphorylation activation and deactivation.
6. Synthesis of nucleic acids: Synthesis of DNA and RNA requires ATP molecules for the formation of phosphodiester bonds between nucleotides.
7. Cell signalling: Signal transduction pathways requires ATP, which aid in influencing the cellular responses to external signals. For example kinase enzyme which performs phosphorylation requires ATP for the addition of phosphate group.
8. Neurotransmitter: In various neurotransmission ATP acts as a signalling molecule.

Functions of ATP

The function of ATP includes:

1. Cellular respiration: ATP is formed through a process known as glycolysis, Krebs cycle, etc in mitochondria of the cell.
2. Contraction of muscles: Muscle fibres require energy for contraction, this energy is delivered by hydrolysis of ATP molecule.
3. Transportation of molecules: Active transport requires ATP for transportation of molecules against the concentration gradient .
4. Biomolecule synthesis: Synthesis of DNA, RNA, protein and lipid requires ATP.
5. Cellular signaling: In cell signaling, phosphorylation by kinase enzyme requires ATP.

Other Energy Molecules

The other energy molecules include:

1. Adenosine diphosphate (ADP): It is also known as adenosine pyrophosphate. Its two phosphate groups makes it different from ATP. Energy is released when a phosphate group is lost from ATP which results in the formation of ADP.
2. Adenosine monophosphate (AMP): It is also known as 5′- adenylic acid and has only one phosphate group. It is found in RNA and formed during the breakdown of RNA and ATP.
3. Cyclic adenosine monophosphate (cAMP): cAMP is an additional energy molecule that is employed for signal transduction and activation of protein kinases. It is produced from ATP and decomposable into AMP. Some malignancies like carcinoma may be influenced by cAMP pathways.

How is Energy Produced By the ATP Molecules?

ATP consists of three phosphate groups. This group is known as high-energy bonds as while utilization of ATP, it releases high energy. Hydrolysis is the process through which ATP releases its energy. Hydrolysis brings H₂O in reaction which breaks down the second and third phosphate bonds in ATP thus leading to formation of ADP and organic phosphate (Pi). ATP reaction is catalyzed by the enzyme ATPase. The process of ATP is exergonic i.e., releases energy outside.

ATP + H₂O → ATPase → ADP + Pi

This molecule is essential to the existence of life itself and provides energy for a variety of biological functions.

Chemical Properties of ATP

ATP is a versatile molecule and has various chemical properties, which makes it an excellent molecule for storing energy and performing biological processes. The chemical properties of ATP are:

1. It is stable at the pH range of 6.8 to 7.4.
2. At extreme pH, it gets hydrolyzed into ADP and phosphate.
3. ATP has a strong phophoanhydride bond in its phosphate group.
4. It has adenine nucleotide, ribose sugar and phosphate group.
5. ATP can interact with Mg ions.

Synthesis of ATP

ATP is produced through three processes in eukaryotes which include:

• Glycolysis: Takes place in the cytoplasm. Breaks down glucose into pyruvate, producing a small amount of ATP.
• Citric acid cycle: Takes place in the mitochondria. Completes the oxidation of glucose-derived molecules, generating NADH and FADH2.
• Electron Transport Chain (Oxidative Phosphorylation): Takes place in the inner mitochondrial membrane. High-energy electrons from NADH and FADH2 transfer through protein complexes, creating a proton gradient. ATP is synthesized as protons flow back into the mitochondrial matrix through ATP synthase.
• Beta oxidation: Takes place in the mitochondria. Breaks down fatty acids to produce acetyl-CoA, which enters the citric acid cycle.

Conclusion

In conclusion, ATP is essential for a variety of biological functions, including the functioning of living cells. It also plays a key role in the transfer of energy inside cells. It is an energy currency molecule to provide energy. It is composed of adenine, ribose sugar and phosphate group. ATP hydrolysis give rise to ADP and organic phosphate. ATP is required in phosphorylation reactions.

FAQs – Structure and Function of ATP

1. What are the 3 Functions of ATP?

ATP is the principal energy currency in living cells. This vital molecule powers crucial biological processes, including muscle contraction, transmission of nerve impulses, and protein synthesis.

2. What is the Function of ATP in Plants?

ATP acts as the primary energy currency, facilitating various biological processes, including photosynthesis, cellular respiration, active transport, and the synthesis of macromolecules, crucial for plant growth, development, and adaptation to environmental changes.

3. What is ATP and its Types?

ATP is high-energy molecule serving as the primary energy currency in cells. ATP and its related molecules, such as GTP (Guanosine Triphosphate), serve as energy carriers in cellular processes

4. Where is ATP Stored?

Upon synthesis, ATP can either reside within the mitochondrial matrix or undergo transport into the intermembrane space (IMS) facilitated by the nucleotide exchanger known as adenine nucleotide translocase (ANT). This transporter facilitates a passive exchange between ATP and ADP.

5. Why is the Function of ATP and Why is it Important?

ATP functions as the cellular reservoir of energy, allowing cells to store energy and release it when needed. Essentially, ATP bridges the gap between energy-releasing reactions, such as the breakdown of food, and energy-demanding processes, such as synthesis.