Zadanie 9, Paper 2, listopad 2025, TZ1, Biologia IB HL
Wzorowane na: Biology HL Paper 2, November 2025, TZ1, pytanie 9. Treść, dane i kontekst są zmienione; sprawdzane umiejętności, format i punktacja jak w oryginale.
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Zadanie
Polecenie
A physiology course examines how biological systems preserve stable information and internal conditions.
(a) Explain mechanisms that reduce copying errors during DNA replication.
(b) Describe regulation of blood glucose in humans.
(c) Explain why extracellular fluids surrounding human cells should be isotonic to the cells.
One additional mark is available for clear, concise construction of the complete response.
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(a) Maximum 4:
Complementary pairing favours the correct nucleotide. ✔
Adenine pairs with thymine and cytosine with guanine. ✔
Each original strand provides a template in semiconservative replication OR this produces the correct copied sequence. ✔
DNA polymerase adds nucleotides to the growing strand. ✔
Proofreading corrects replication mistakes. ✔
DNA polymerase performs proofreading OR detects a mismatched base. ✔
Its3′→5′ exonuclease removes an incorrect nucleotide OR the incorrect nucleotide is removed and replaced. ✔
(b) Maximum 7:
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) Maximum 4:
Isotonic fluids have an effective osmotic concentration matching that of the cells. ✔
This prevents sustained net osmotic water movement. ✔
Hypotonic extracellular fluid drives water into cells. ✔
Cells may swell OR lyse. ✔
Hypertonic extracellular fluid draws water out of cells. ✔
Cells shrink or crenate. ✔
Blood cells are surrounded by plasma. ✔
Tissue fluid is released through capillaries and subsequently reabsorbed OR it bathes or flows between tissue cells. ✔
Construction:1 mark for clear, concise, well-organized communication across the response, without substantial repetition or irrelevant material.
Schemat punktowania
Parts(a),(b),(c):any4,7,4 distinct points respectively, max15 content marks. Add1 independent construction mark; total16. All printed Section B alternatives are retained as separate tasks. In the stated cell context, matching water/solute/osmotic potential is an accepted description of isotonic conditions; higher or less-negative external water potential may replace hypotonic, and lower or more-negative may replace hypertonic. These descriptions assume the relevant effective solutes and pressure conditions. 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.