They mobilize the cell. So we see that although centrioles are not exactly necessary for the survivor of the individual cell the centrioles and centrosomes are necessary for the survival of the organism as a whole. For example, if we examine a specific type of cell that needs flagella our sperm cells. If our sperm cells do not have centrioles or centrosomes, they cannot form our basal body and they cannot form the flagella. And a sperm cell without a flagella will not be able to reach the target cell. And that means our organism will essentially die off.