The seminal vesicles contribute nearly 60 percent of the volume of seminal fluid. These secretions are an alkaline fluid containing water, fructose, prostaglandins, and clotting proteins. The fructose provides an energy source for the sperm. Prostaglandins contribute to sperm motility and viability. The clotting proteins help semen coagulate after ejaculation. The alkalinity of the fluid helps to neutralize the acidic environments of the male urethra and female reproductive tract.