A haploid cell is a cell typically with half the number of chromosomes (a sex cell) used for reproduction.
A diploid cell is the opposite, a full set of chromosomes not intended for sexual reproduction but typically used in mitosis.
Through phosphorylation, Cdks signal the cell that it is ready to pass into the next stage of the cell cycle. As their name suggests, Cyclin-Dependent Protein Kinases are dependent on cyclins, another class of regulatory proteins. Cyclins bind to Cdks, activating the Cdks to phosphorylate other molecules.
