The goal of a sperm is to simply swim up through the female reproductive tract, penetrate egg and deliver paternal DNA. Sperm cells have very little cytoplasm- so might be missing some protective mechanisms that other cells have and they rely on the seminal fluid for protection and nutrients.
Removal of cholesterol and increases permeability to Ca which increase cAMP levels which increase motility.
An acrosome is an organelle that develops over the head in the spermatozoa. This organelle contains digestive enzymes that break down zona pellucida. The shedding of this is called acrosome reaction- stimulated by follicular fluid or progesterone?