Zadanie 6, Paper 2, listopad 2025, TZ1, Biologia IB SL
Wzorowane na: Biology SL Paper 2, November 2025, TZ1, pytanie 6. Treść, dane i kontekst są zmienione; sprawdzane umiejętności, format i punktacja jak w oryginale.
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Zadanie
Polecenie
Feedback regulates physiological variables.
(a) Discuss positive and negative feedback in variable control.
(b) Describe the regulation of human blood glucose.
(c) Explain responses expected when blood pH falls below its usual range.
One additional mark is available for clear, concise construction of the complete response.
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Pokaż rozwiązanieUkryj rozwiązanieKlucz i punktacja
Odpowiedź z klucza
(a) Maximum4:
Negative feedback maintains homeostasis or equilibrium. ✔
It returns a variable towards a set point. ✔
It keeps variables within a narrow range. ✔
An increase evokes a decrease, and a decrease evokes an increase. ✔
Positive feedback amplifies a change. ✔
Positive feedback moves a system away from equilibrium. ✔
Positive feedback usually operates for a limited period. ✔
(b) Maximum7:
Pancreatic cells detect blood-glucose concentration. ✔
Alpha cells secrete glucagon and beta cells secrete insulin. ✔
These hormones travel in the bloodstream. ✔
High blood glucose stimulates insulin release. ✔
Insulin promotes glucose uptake by muscle or other responsive cells OR net hepatic glucose uptake/storage. ✔
Insulin favours glycogen synthesis (for example in liver or muscle). ✔
Insulin promotes glucose use rather than fat use in respiration. ✔
Low blood glucose stimulates glucagon release. ✔
Glucagon promotes conversion of glycogen to glucose (in the liver). ✔
Negative feedback brings blood glucose back towards the regulated range. ✔
(c) Maximum4:
Raised blood CO₂ can lower pH OR removing CO₂ raises pH. ✔
Chemoreceptors detect increased acidity. ✔
The brainstem controls ventilation. ✔
Diaphragm or intercostal contractions become more frequent or stronger. ✔
Ventilation increases. ✔
More carbon dioxide is removed through alveolar gas exchange. ✔
Cardiac contractions may become more frequent or stronger. ✔
Blood pressure or blood flow may increase. ✔
Construction:1 mark for clear, concise communication across the complete response.
Schemat punktowania
Parts(a),(b),(c):max4,7,4 respectively. Maximum15 content plus1 independent construction mark, total16. Part(a):cap negative-feedback points at3, requiring positive feedback for4. In (b), the site of glycogen synthesis and the liver site of glucagon action are optional details; glucose release is not an additional requirement for the glycogen-breakdown point. Do not credit a claim that glucagon directly stimulates muscle glycogen breakdown.