Question

Which organelle is absent in human sperm?
A. Mitochondria
B. Nucleus
C. Centriole
D. E.R.

Answer 1

Hint: Human sperms are gametes of the male reproductive system. These possess head, neck and tail portions. Sperms consist of subcellular organelles such as mitochondria, centriole and nucleus.

Complete answer:
The testis is the primary sex organ in males that develop gametes, i.e. sperm. The mature sperm cell consists of a head, a spine, a tail, and a middle section. The entire body of sperm is enveloped by a plasma membrane. There is a very small amount of cytoplasm in the sperm head, the anterior part of which is protected by an acrosome cap. It has an elongated haploid nucleus. There are two distinct granules in the short neck, viz. the proximal and distal centrioles. During the first cleavage of the fertilized ovum, the proximal centriole plays a critical part. The distal centriole gives rise to the sperm’s long tail axial filament. There are multiple mitochondria in the middle portion of a mammalian sperm cell. They generate energy for sperm cell movement. However, sperms do not contain endoplasmic reticulum. The endoplasmic reticulum is present in all other cells except sperms. Membrane-bound cell organelles are mitochondria which generate most of the chemical energy required to power the biochemical reactions of a cell.

Hence, the correct answer is option D.

Note: Sperms are produced by spermatogenesis; it is the mechanism by which haploid spermatozoa arise from germ cells. Sperms do not require synthesizing any protein and this is probably the reason that they do not possess any E.R.