Adenosine triphosphate (ATP)
Where does the cell get the energy required to produce ATP?
The energy needed to attach a phosphate group to ADP is supplied mainly by the catabolism of glucose in a process called cellular respiration. Cellular respiration has two phases, anaerobic and aerobic
As the supply of ATP at any given time is limited, a mechanism exists to replenish it:
The enzyme ATP synthase catalyzes the addition of a phosphate group to ADP
Structures of ATP and ADP
"Squiggles" (~) indicate the two phosphate bonds that can be used to transfer energy.
The enzyme that catalyzes the hydrolysis of ATP is called
ATPase
Anaerobic phase.
In a series of reactions that do not require oxygen, glucose is partially broken down by a series of catabolic reactions into pyruvic acid. Each glucose molecule that is converted into a pyruvic acid molecule yields two molecules of ATP.
Aerobic phase.
In the presence of oxygen, glucose is completely broken down into carbon dioxide and water. These reactions generate heat and 30 or 32 ATP molecules.
Removal of the third phosphate group produces a molecule called
adenosine diphosphate (ADP)
As noted previously, the energy supplied by the catabolism of ATP into ADP is
constantly being used by the cell.
Energy transfer typically involves
hydrolysis of the last phosphate bond of ATP.
When a water molecule is added to ATP, the third phosphate group
is removed, and the overall reaction liberates energy.
Adenosine triphosphate (ATP)
is the "energy currency" of living systems
Among these cellular activities are
muscular contractions, movement of chromosomes during cell division, movement of structures within cells, transport of substances across cell membranes, and synthesis of larger molecules from smaller ones.
ATP transfers chemical energy to
power cellular activities
ATP transfers the energy liberated in exergonic catabolic reactions to
power cellular activities that require energy (endergonic reactions).
As its name implies, ATP consists of
three phosphate groups attached to adenosine, a unit composed of adenine and the five-carbon sugar ribose.