Final answer:
Capacitation is a process that sperm undergo after ejaculation, taking several hours, to become capable of fertilizing an oocyte. This involves alteration of motility and membrane structure, occurring as sperm travel through the female reproductive tract towards the oocyte.
Step-by-step explanation:
The process of capacitation is essential for the ability of sperm to fertilize an oocyte. After ejaculation, fluids within the female reproductive tract help prepare the sperm for fertilization, a journey that can take from 30 minutes to 2 hours to reach the oocyte. Importantly, capacitation alters the sperm's motility and membrane structure, specifically depleting cholesterol molecules to facilitate the acrosomal reaction necessary for penetrating the oocyte's outer layers. Without capacitation, which takes approximately several hours after the sperm enter the female reproductive tract, sperm are unable to fertilize the oocyte.
Furthermore, if intercourse occurs a few days before ovulation, the sperm can survive in the uterine tubes for about 3-5 days, which means fertilization can still occur within this timeframe. However, for a sperm to become fully capacitated and ready to fertilize an oocyte, fertilization can only occur after sufficient time has passed for the completion of the capacitation process.