Zadanie 10, Paper 2, maj 2026, TZ1, Biologia IB HL
Wzorowane na: Biology HL Paper 2, May 2026, TZ1, pytanie 10. Treść, dane i kontekst są zmienione; sprawdzane umiejętności, format i punktacja jak w oryginale.
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Zadanie
Polecenie
Membranes support water balance, electrical signalling and energy conversion.
(a) Outline what happens to cells in a piece of plant tissue transferred to a hypotonic solution.
(b) Describe the establishment and maintenance of a resting membrane potential in a neuron.
(c) Explain how mitochondrial electron transport contributes to ATP production in aerobic respiration.
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Odpowiedź z klucza
(a) Water enters the plant cells by osmosis. ✔
Net movement follows the water-potential difference from the dilute surroundings into the cells. ✔
The expanding contents press against the cell wall. ✔
Positive pressure potential develops within the cell. ✔
The cells become turgid as wall resistance limits further expansion. ✔
(b) A typical resting potential is about −70 mV. ✔
The inside is electrically negative relative to the outside. ✔
ATP hydrolysis provides energy for active ion transport. ✔
Sodium–potassium pumps operate in the membrane. ✔
Each cycle moves three Na⁺ out and two K⁺ in. ✔
This maintains unequal ion distributions across the membrane. ✔
Selective ion permeability, particularly potassium leakage, contributes to the negative interior. ✔
(c) Glycolysis, the link reaction and the Krebs cycle supply high-energy electrons. ✔
Reduced NAD carries electrons and donates them to the chain. ✔
Oxidation of respiratory substrates forms reduced electron carriers. ✔
Electrons pass through a sequence of carriers in the inner mitochondrial membrane. ✔
Energy released in these transfers drives proton pumping. ✔
Protons move from the matrix into the intermembrane space. ✔
A proton electrochemical gradient is established. ✔
Protons return towards the matrix down this gradient. ✔
Their return through ATP synthase drives the enzyme. ✔
ATP synthase couples this flow to ADP phosphorylation. ✔
Oxygen accepts electrons at the end of the chain. ✔
Oxygen combines with electrons and protons to form water. ✔
The proton-gradient coupling is chemiosmosis. ✔
Oxidative phosphorylation supplies the majority of ATP made during aerobic respiration. ✔
Schemat punktowania
(a) Award any 4 listed points; maximum 4. (b) Award any 4 listed points; maximum 4. The numerical resting voltage and the relative negative charge are separate accepted points, following the source scheme. (c) Award any 7 listed points; maximum 7. Quality: award 1 additional mark for a response across all three parts that is readily understandable, concise and largely free of repetition or irrelevant material. Judge this independently of content marks. Maximum 16 marks overall.