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Figure 5 shows the level of progesterone for a female during five different stages of the menstrual cycle - Edexcel - GCSE Biology Combined Science - Question 5 - 2016 - Paper 1
Question 5
Figure 5 shows the level of progesterone for a female during five different stages of the menstrual cycle. | days in the menstrual cycle | progesterone level (nmol/... show full transcript
Worked Solution & Example Answer:Figure 5 shows the level of progesterone for a female during five different stages of the menstrual cycle - Edexcel - GCSE Biology Combined Science - Question 5 - 2016 - Paper 1
Step 1
Describe the changes in progesterone levels during the 28-day cycle.
Answer
During the first nine days of the menstrual cycle, progesterone levels are relatively low at 1.85 nmol/l.
From days 10 to 14, there is a slight decrease in progesterone levels to 1.48 nmol/l. This marks the follicular phase when estrogen is more dominant.
However, from days 15 to 17, progesterone levels rise significantly to 14.28 nmol/l, indicating the start of the luteal phase as the corpus luteum forms and begins to produce progesterone.
The peak is observed between days 18 and 23 with progesterone reaching 35.27 nmol/l, which supports the potential implantation of an embryo.
Finally, from days 24 to 28, progesterone levels drop to 17.11 nmol/l, signaling the end of the luteal phase as the corpus luteum degenerates if fertilization does not occur.
Step 2
Explain why progesterone levels changed following day 14.
Answer
Following day 14, progesterone levels changed due to the transition into the luteal phase of the menstrual cycle. After ovulation occurs around day 14, the ruptured follicle transforms into the corpus luteum, which secretes progesterone. This hormone is critical for preparing the uterine lining for possible implantation of a fertilized egg. The notable increase in progesterone levels is crucial for maintaining early pregnancy if fertilization occurs, and its decline is responsible for the onset of menstruation if fertilization does not take place.