Final answer:
The seminal vesicle is the male gland that secretes fructose sugar for sperm energy. It produces an alkaline, fructose-rich fluid that forms most of the semen, which is essential for sperm motility and survival.
Step-by-step explanation:
The male gland that secretes a fructose sugar used as an energy source for sperm is the seminal vesicle. This gland is part of the male reproductive system and is responsible for producing a significant portion of the semen's volume.
The seminal vesicle makes a thick, yellowish solution that is alkaline, which is necessary for sperm motility by creating a favorable environment that counters the acidity of the vaginal environment.
This solution contains a variety of substances including mucus, fructose, a coagulating enzyme, ascorbic acid, and prostaglandins.
Fructose is especially important as it serves as a critical energy source, fueling the sperm's long journey for potential fertilization.
While the prostate gland also contributes to the formation of semen, it is the seminal vesicles that predominantly produce the fructose-rich fluid.