The cell (life) cycle is the period of the existence of a cell from the moment of formation by division of the mother cell to its own division or death.
In different types of organisms, the cell cycle takes different time: in prokaryotes it lasts 20 – 30 minutes, and in eukaryotic cells it can last from 10 to 20 hours. In young organisms, cells divide frequently, and then gradually the time between divisions lengthens. Some cells generally lose the ability to divide (neurons, heart muscle cells).
The cell cycle consists of interphase and division.
Interphase is the period of cell life between two divisions.
During interphase, the cell performs its functions and prepares for division. The most important process is DNA duplication (replication).
The DNA molecule is unwound with the help of a special enzyme into two strands. The enzyme breaks hydrogen bonds between complementary nitrogenous bases.
The DNA strands are diverging.
The enzyme DNA polymerase adjusts a complementary nucleotide to each nucleotide of the disconnected DNA strands.
The adjusting nucleotides are linked to each other.
As a result, two double DNA molecules are formed, each of which is an exact copy of the original DNA.
In the interphase, there is also an accumulation of ATP, an increase in the number of organelles, and the synthesis of substances necessary for the formation of a fission spindle.