ATP (Adenosine triphosphate)
Adenosine triphosphate is complex organic molecule which carries energy within cells. It is considered as energy currency and store house of cells by the biologists. ATP is the end product molecule of Phosphorylation, Cellular Respiration and Fermentation.
- Living cells acquire energy by the breakdown of complex molecules such as polysaccharides, fats, proteins, alcohols etc. Phototrophs utilizes sunlight whereas chemotrophs utilizes the chemical compounds as their source of energy. A lot of energy is released on degradation of complex molecules which is captured in the cell (in the form of chemical bonds that can be utilized readily when needed).
In the cell, energy is captured in the form of adenosine triphosphate (ATP) while rest of those which is not captured in lost as heat.
ATP is composed of Adenosine (Adenine + Ribose sugar) along with three phosphate groups. It is nucleotide consisting of adenine, pentose sugar ribose and a triphosphate unit. Adenine is attached to first carbon and Phosphate groups are esterified at fifth carbon atom of ribose.
- It is activated by cations such as Mg 2+ and Mn2+. When complexed with these cations it gets activated. The energy is stored in its triphosphate moiety.
Release of energy occurs on hydrolysis of ATP to ADP (Adenosine di-phosphate) and Pi (Inorganic phosphate) which is utilized for various purposes. Sometimes, ATP is hydrolysed to AMP and pyrophosphate (PP).
- Even though ATP are continuously utilized by the cells as energy source, it is constantly synthesized from ADP (Adenosine di-phosphate) and phosphate.
- These enzymes are found in membranes of mitochondria of animal cells (Reason why mitochondria is powerhouse of the cell) and chloroplasts in plant cells.
The central role of ATP in energy metabolism was discovered by Fritz Albert Lipmann and Herman Kalckar in 1941.
In human body, total ATP accounts for 0.1 mole. Energy used daily by an adult demands hydrolysis of 200 to 300 moles of ATP i.e. Each ATP molecule has to be recycled 2000 to 3000 times.
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