Given below is the diagram of a human sperm. Read the information below the diagram and fill in the blanks: [The paper prints a labelled diagram of a human sperm above this passage. Refer to the diagram supplied with this question.]
Fill in the blanks (a) to (e) with reference to the diagram of the human sperm: (a) The cap-like structure covering the head of the sperm is the __________. (b) The enzyme produced by it is __________. (c) The nucleus of the sperm contains __________ chromosomes. (d) The middle piece contains __________, which supply energy for motility. (e) The mixture of sperms and the secretions of the male accessory glands is called __________.
Topic: Structure of the human sperm
Answer
(a) Acrosome (b) Hyaluronidase (c) 23 (d) Mitochondria (e) Semen
One mark per blank. Work through the sperm from head to tail, because the diagram is drawn in that order and so are the blanks.
(a) The ACROSOME is the cap over the front of the head, derived from the Golgi body.
(b) It contains HYALURONIDASE, an enzyme that dissolves the follicular cells and the membrane around the ovum so that the sperm can penetrate it. Without it fertilisation cannot occur.
(c) TWENTY-THREE. This is the commonest error in the question. A human body cell has 46 chromosomes (23 pairs), but a gamete is HAPLOID — it carries 23 single chromosomes, so that when sperm and ovum fuse the zygote has the full 46 again. Write 23, not 23 pairs.
(d) MITOCHONDRIA, packed spirally into the middle piece. They respire to release the ATP that drives the lashing of the tail, which is why the middle piece is sometimes called the powerhouse of the sperm.
(e) SEMEN — sperms together with the secretions of the seminal vesicles, prostate gland and Cowper’s glands, which nourish the sperm and provide the fluid medium they swim in.
THE STRUCTURE-FUNCTION LINK worth carrying into any question on the sperm: head = genetic material plus the enzyme to get in; middle piece = energy; tail = movement.