Semen facts Most of the ejaculate is made up of the fluid that supports the sperm. Besides sperm, semen is made up of fluids; 65% from the seminal vesicles, 30 to 35% from the prostate and 5% from the vasa. Semen contains citric acid, free amino acids, *fructose, enzymes, phosphorylcholine, prostaglandin, potassium, and zinc