Semen is a mixture of sperm and secretions of seminal vesicle, prostate gland and Cowper's gland. The molecules present in the semen includes sperm amino acids, proteins, lipids, Anti-sperm antibodies and trace elements like include zinc, megnesium, sodium and potasium. Each of these molecules is having specific function. Trace elements play a major impact on the quality of the semen and inturn, these trace elements helps in motility, metabolism, and acrosome reaction. The cumulative function of all these molecules determines the quality of semen to accomplish the task of fertilization. Due to increased industralization and environmental pollution over the past decades, numerous studies have reported that a decline in semen quality in men in various parts of the world has been observed. Besides, the semen quality and acticity is reported to be declined 50% between 1930 and 2011. There are several proteins identified in the semen that are used as a biomarker, acting as an identification marker for fertility of an individual. The seminal plasma proteins are identified to help in transport and elimination in female reproductive tract. Reactive oxygen species (ROS) are identifide to be present even in the normal semen (15%), and it is found to be increasing in the infertile samples. So, in this review paper we have dissused about the effects and functions of the various micro and macromolecules in the semen to make the future generation alert on the male infertility.