What is the full form of ATP

ATP: Adenosine Triphosphate

ATP stands for Adenosine Triphosphate. It is a high-energy molecule found in the cells of the human body, animals, plants, etc. It is capable of storing and supplying the energy needed by cells. So, it is commonly known as the energy currency of the cell.

The human body is made up of different types of cells. Each type of cell performs a specific function that helps organisms to perform tasks necessary for survival. For example, nerve cells communicate messages to the brain and allow us to think, make decisions and more. Similarly, muscle cells help us to produce force and motion, maintain posture and contraction of organs, and more. Cells need the energy to perform these tasks, which is provided by ATP.

The food that we eat is gradually oxidized in the cells, and energy is released, which is used to produce the ATP so that a continuous supply of ATP is maintained. In simple words, we store the energy obtained from the breakdown of food as ATP. Similarly, plants store energy produced during photosynthesis in ATP molecules.

Structure of ATP:

ATP is a nucleotide which is made up of an adenosine molecule (adenine base attached to a ribose sugar), which is further connected to three phosphate groups by phosphoanhydride bonds. So, it has three main parts: adenine (a nitrogenous base), sugar (ribose), and triphosphate (three phosphate groups). These parts are connected into a single molecule through condensation reactions. When only one phosphate group is attached, this compound is known as adenosine monophosphate (AMP); when one more group is attached, it becomes adenosine diphosphate (ADP), and when the third one is added, adenosine triphosphate (ATP) is formed.

The phosphate groups are attached to one another by phosphoanhydride bonds. When energy is needed by the cells, the third phosphate group is removed, and only two phosphate groups are left behind. For example, during hydrolysis, the enzyme ATPase hydrolyses the bond between the second and third phosphate groups in ATP. We can say that the ATP molecule is hydrolysed into adenosine diphosphate (ADP) and an inorganic phosphate ion with the release of chemical energy. Similarly, energy is released when one more phosphate is removed from ADP, and adenosine monophosphate (AMP) is formed.

However, AMP can be converted into ADP or ATP through new phosphoanhydride bonds to store energy. So, in a cell, ATP, AMP and ADP are continuously interconverted through biological reactions. ATP is constantly consumed and regenerated to ensure that an organism can function and survive.

How is ATP Produced?

ATP is produced during cellular respiration that occurs in the cytosol and mitochondria of a cell. This process begins with glycolysis and is followed by aerobic respiration, which comprises the Krebs' Cycle and the electron transport chain. So, there is a total of three steps that create a total of 36 ATP molecules: 2 ATP molecules are produced in glycolysis, 2 are produced in the Krebs' Cycle and 32 are produced by the electron transport chain.

ATP is also produced in plants through photosynthesis, in which light and dark reactions occur. In the light reaction, the energy of the sun is converted into chemical energy in the form of ATP through the phosphorylation of ADP, which take on a phosphate group to become ATP. In the dark reaction of photosynthesis, which is called the Calvin Cycle, the same ATP is used to synthesize glucose needed by plants to survive.

ATP is used in different ways and for thousands of different purposes in humans, animals, plants, etc. ATP moves through diffusion (from high concentration to low concentration) to the area where it is required for energy, and the energy is released when the bond between the second and third phosphate groups breaks down, and a phosphoryl group is removed.

Functions

Energy is required for a variety of vital biological and cellular functions, including ATP hydrolysis. These include active transport, Purinergic signalling, synaptic signalling, intracellular signalling, DNA and RNA synthesis, and muscular contraction. Although not a complete list, these subjects cover some of the crucial functions that ATP plays.

Intracellular Signalling Using ATP

On ATP, signal transduction largely depends. The most common ATP-binding protein, kinases, can use ATP as a substrate. A signalling cascade can be started when a kinase phosphorylates a protein, which can then modulate a variety of intracellular signalling pathways. Because kinase activity is essential to the cell, it must be strictly controlled. The magnesium ion's presence aids in controlling kinase activity. Magnesium ions, which are present in the cell in a combination with ATP and are bonded at the phosphate oxygen centres, are regulated. ATP can operate as a common trigger of intracellular messenger release in addition to kinase activity. Hormones, different enzymes, lipid mediators, neurotransmitters, nitric oxide, growth factors, and reactive oxygen species are a few of these messengers. Adenylate cyclase uses ATP as a substrate, which is an illustration of how ATP is used in intracellular signalling. Most often, G-protein coupled receptor signalling pathways are involved in this process. Adenylate cyclase's conversion of ATP into cyclic AMP helps trigger the release of calcium from intracellular reserves. Other functions of cAMP include activating protein kinases, serving as secondary messengers in hormone signalling cascades, and controlling ion channel activity.

Synthesis of DNA/RNA

The production of DNA and RNA needs ATP. One of the four nucleotide-triphosphate monomers required for RNA synthesis is ATP. Identical methods are utilized during the creation of DNA; however, during this process, ATP is first modified by eliminating an oxygen atom from the glucose to create deoxyribonucleotide or dATP.

The Purinergic Signalling

Purine nucleotides, such as ATP, are the mediators of purinergic signalling, a type of extracellular paracrine signalling. Purinergic receptors on nearby cells are frequently activated during this process, allowing signals to control intracellular activities to be transmitted. A universal exocytotic regulatory mechanism called IP3 controls the release of ATP from vesicular storage. The fact that neurotransmitters store and release ATP simultaneously supports the idea that ATP is an essential modulator of purinergic neurotransmission in both sympathetic and parasympathetic neurons. In addition to controlling autonomic activities, brain glia interactions, pain, and vascular tone, ATP can also cause various other purinergic reactions.

Muscle Contraction Using ATP

Without ATP, muscle contraction would not be possible, which makes it an essential bodily function. ATP participates in the process of muscle contraction in three main ways. The first method involves cycling myosin cross-bridges to produce force against nearby actin filaments. In the latter, calcium ions from the myoplasm are actively transported throughout the sarcoplasmic reticulum in defiance of concentration gradients. When an input is received, calcium ions can be suspended due to the sarcolemma's active sodium and potassium ion transport. This is the third job that ATP does. Each of these steps is propelled by the hydrolysis of ATP.

Clinical Importance

ATPs' Function in Pain Management

Clinical trials on ATP show a decrease in acute perioperative discomfort. Patients in these studies received intravenous ATP. The intravenous infusion of adenosine interacts with the A1 adenosine receptor and sets off a signalling cascade that ultimately contributes to the pain-relieving benefits seen in inflammation. Adenosine compounds have been demonstrated in studies to lessen allodynia and hyperalgesia when used in moderate concentrations. A1 adenosine receptor activation produces efficient pain relief because it has a gradual onset and a lengthy half-life, sometimes lasting for weeks.

Anaesthesia

During anaesthesia, ATP supplementation provided beneficial results. Evidence suggests that neuropathic pain, ischemic pain, and hyperalgesia are reduced by low doses of adenosine to an extent comparable to morphine. Adenosine also reduced the need for postoperative opioids, pointing to a potential long-lasting activation of the A1 adenosine receptor.

Surgery and Cardiology

In individuals with pulmonary hypertension, ATP has been shown to be a reliable and safe pulmonary vasodilator. Adenosine and ATP can also be used to lower a patient's blood pressure during surgery.