some hormones, such as ADH, act only on specific target cells (in this case those of the kidneys), while others, such as insulin, are able to affect all cells in the body. What is the biological principle behind this difference?

haploid cells;

both male and female gametes are produced by meiosis of the germ cells. therefore, both male and female gametes are haploid. one male and one female gamete unite during the fertilization to form the diploid zygote. in seed bearing plants, pollen grain is the male gametophyte, which produces sperm cells.

a scenario where a cell may be needed to perform a form of endocytosis is when transporting large molecules. a scenario where a cell may be needed to perform a form of exocytosis is when releasing the large molecule from the cell.