Why is ARP required

What is ATP

Model: © Susanne Bickel

The ATP ball-bar model (left) and the structural formula (right)

ATP is the universal form of storage for chemical energy in cells. When the phosphate groups are split off, ADP and Pi (inorganic phosphate) are formed. This reaction is strongly exergonic, i.e. energy is released (30.5 kJ / mol). This energy is made usable for the cell through energetic coupling to processes such as biosynthesis (e.g. in the Calvin cycle) as well as movement and transport processes. These processes are endergonic, i.e. they only take place when there is a supply of energy.ATP works in the metabolism by transferring its phosphate group to other substances (e.g. sugar). These can only be changed (e.g. split) if they contain at least one, sometimes two phosphate groups. ATP / ADP can exercise its function in the metabolism because it is in the middle of the series of phosphate-transferring substances in terms of phosphate transfer potential. It must be able to release phosphate groups and be able to accept them again. By adopting a phosphate group, ADP becomes ATP again.

What is ATP used for?

ATP drives cellular work by coupling exergonic and endergonic partial reactions. The energy from ATP hydrolysis is coupled directly to endergonic (energy-consuming) processes by various enzymes, or a phosphate group is transferred from ATP to another molecule.
Carbon dioxide is fixed in the Calvin cycle. That is, the inorganic CO2 from the air, an enzyme (ribulose bisphosphate carboxylase, RubisCo for short) is bound to an existing substance (ribulose diphosphate). The plant needs energy for this. This comes from the light-dependent reaction, i. H. from the ATP formed there.
 Task: Take your textbook to hand and consider: What functions do we need ATP for? Do you know reactions that require ATP? What do humans and animals do to gain ATP?