Adenosine triphosphate (ATP) is a multifunctional nucleotide used in cells as a coenzyme. It is often called the “molecular unit of currency” of energy transfer. ATP transports chemical energy within cells for metabolism. It is produced by photo-phosphorylation and cellular respiration and used by enzymes and structural proteins in many cellular processes, including active transport, respiration, and cell division. One molecule of ATP contains three phosphate groups, and it is produced by ATP synthase from inorganic phosphate and adenosine diphosphate (ADP).
ATP is used is many organisms and also in different ways. Below are a few ways in which ATP is used. When muscles contract in any organism, it means muscle fibers are generating tension with the help of motor neurons. ATP is the source of energy that allows this to take place. Voluntary muscle contraction is controlled by the central nervous system. The brain sends signals, through the nervous system to the motor neuron that innervates several muscle fibers. In the case of some reflexes, the signal to contract can originate in the spinal cord through a feedback loop with the grey matter.
Involuntary muscles such as the heart or smooth muscles in the gut and vascular system contract as a result of non-conscious brain activity or stimuli proceeding in the body to the muscle itself. The organism will respire more as much more energy will be needed, in the form of ATP. ATP is also used in Active transport. This is the movement of a substance against its concentration energy (from low to high concentration). In all cells, this is usually concerned with accumulating high concentrations of molecules that the cell needs, such as ions, glucose, and amino acids.
Active transport is a good example of a process for which cells require energy: adenosine triphosphate (ATP). Examples of active transport include the uptake of glucose in the intestines in humans and the uptake of mineral ions into root hair cells of plants. Specialised trans-membrane proteins recognize the substance and allows it access to cross the membrane when it otherwise would not, either because it is one to which the phospholipid bilayer of the membrane is impermeable or because it is moved in the direction of the concentration gradient.
The last case, known as primary active transport, and the proteins involved in it as pumps, normally uses the chemical energy of ATP. The other cases, which usually derive their energy through exploitation of an electrochemical gradient, are known as secondary active transport and involve pore-forming proteins that form channels through the cell membrane. Sometimes one substance is transported in one direction at the same time as another substance is transported in the other direction. This is called Co- transport.
In Co-tansport one of the two substances are transported in the direction of their concentration gradient utilizing the energy derived from the transport of the second substance (mostly Na+, K+ or H+) down its concentration gradient. Active transport often takes place in the internal lining of the small intestine. Plants need to absorb mineral salts from the soil, but these salts exist in very dilute solution. Active transport enables these cells to take up salts from this dilute solution against the direction of the concentration gradient.
In cellular respiration, the set of the metabolic reactions and processes that take place in organisms cells to convert biochemical energy from nutrients into adenosine triphosphate (ATP), and then release waste products. The reactions involved in respiration are catabolic reactions that involve the oxidation of one molecule and the reduction of another. Respiration is one of the key ways a cell gains useful energy to fuel cellular reformations.