Date | May 2018 | Marks available | 4 | Reference code | 18M.2.HL.TZ1.8 |
Level | Higher level | Paper | Paper 2 | Time zone | Time zone 1 |
Command term | Describe | Question number | 8 | Adapted from | N/A |
Question
Describe the process of spermatogenesis leading to the production of four sperm cells in a human male.
Outline the roles of estrogen and progesterone in females during human reproduction.
Explain the process of muscle contraction.
Markscheme
a. in the seminiferous tubule
b. diploid cells/spermatogonia grow/enlarge
c. two divisions of meiosis
d. primary spermatocyte carries out the first division and secondary spermatocytes carry out the second division
e. meiosis produces haploid cells/spermatids
f. haploid cells/spermatids differentiate into spermatozoa/sperm cells
OR
develop tail/flagellum/helical mitochondrion/acrosome/sac of enzymes
g. Sertoli cells help sperm to mature/differentiate
Allow answers presented in a clearly annotated diagram.
a. estrogen/progesterone for repair/thickening/development/vascularisation of uterus lining/endometrium
b. estrogen (at high levels) stimulates LH secretion (which stimulates ovulation)
c. progesterone maintains the uterus lining/endometrium during pregnancy/prevents miscarriage
d. progesterone/estrogen inhibits FSH/LH secretion
e. progesterone for development of breast tissue during pregnancy
f. fall in progesterone/rise in estrogen leads to labour/contractions/childbirth
g. estrogen/progesterone cause pre-natal development of female reproductive organs
OR
h. estrogen/progesterone cause secondary sexual characteristics
a. muscle fibre contains many myofibrils
b. made up of sarcomeres/labelled diagram showing one or more sarcomeres
c. nerve impulse/signal from (motor) neuron causes release of calcium (ions)/Ca2+
d. calcium (ions)/Ca2+ released from sarcoplasmic reticulum
e. calcium (ions)/Ca2+ link to troponin
f. tropomyosin moves to expose actin binding sites
g. ATP hydrolysis/ATP to ADP and phosphate/release of phosphate from ATP
h. ATP binds to myosin heads and causes them to cock/change angle/release/gain energy
i. myosin heads bind/form cross-bridges to actin
j. myosin heads push on actin and then detach from actin
k. actin moved towards centre of sarcomere/sliding of filaments
l. sarcomere becomes shorter (resulting in muscle contraction)
Accept any mark point if clearly made on an annotated diagram.