Zadanie 6, Paper 2, maj 2023, TZ1, Biologia IB HL
Wzorowane na: Biology HL Paper 2, May 2023, TZ1, pytanie 6. Treść, dane i kontekst są zmienione; sprawdzane umiejętności, format i punktacja jak w oryginale.
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Zadanie
Polecenie
(a) Outline the role of ADH in maintaining water balance.
(b) Explain how an end product can regulate the pathway that makes it.
(c) Describe hormonal feedback involved in preparation for pregnancy, maintenance of pregnancy and childbirth.
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(a)
ADH release increases when the body is dehydrated or blood solute concentration rises. ✔
More aquaporins become available in collecting-duct membranes OR aquaporin-mediated water transport increases. ✔
The collecting duct becomes more permeable to water OR more water is reabsorbed from the filtrate. ✔
Water is reabsorbed by osmosis OR the medulla is hypertonic relative to the filtrate. ✔
Reabsorbed water returns to the blood OR blood solute concentration falls. ✔
Less water is lost in urine OR a smaller urine volume is produced. ✔
This is negative feedback OR ADH release falls as the regulated blood concentration is restored. ✔
(b)
An end product inhibits or slows its own production pathway. ✔
An early enzyme or step is inhibited. ✔
The inhibition is non-competitive OR involves allosteric binding OR changes the active site. ✔
An excess of end product reduces or pauses further synthesis. ✔
Isoleucine inhibits the initial enzyme using threonine in the pathway that makes isoleucine; another verified example is acceptable. ✔
This is negative feedback OR synthesis resumes as product is used and its concentration falls. ✔
(c)
FSH stimulates oestrogen secretion. ✔
Oestrogen can increase follicular responsiveness to FSH, amplifying oestrogen output. ✔
Oestrogen promotes repair and thickening of the endometrium. ✔
High oestrogen promotes the LH surge or inhibits FSH secretion. ✔
The LH surge causes ovulation. ✔
LH supports formation of the corpus luteum OR the corpus luteum secretes progesterone. ✔
Progesterone inhibits further FSH/LH secretion. ✔
Progesterone maintains the endometrium for implantation and pregnancy. ✔
Progesterone suppresses uterine contractions during pregnancy. ✔
Embryonic hCG supports persistence of the corpus luteum early in pregnancy. ✔
Uterine contractions stimulate further oxytocin release, which intensifies contractions. ✔
This positive feedback assists childbirth. ✔
Quality of communication: The whole response is clear on a first reading and concise, with little repetition or irrelevant material. ✔
Schemat punktowania
Part (a): Award any 4 of the listed points; maximum 4 marks. Part (b): Award any 4 of the listed points; maximum 4 marks. Part (c): Award any 7 of the listed points; maximum 7 marks. Award 1 independent quality mark for clear, concise communication across the whole response. Maximum 16 marks. Accept alternative scientifically equivalent examples where the source allows examples; do not require every item joined by OR.