Gce Model Questions Vol1 2023 Biology Question 50

Practice objective / multiple choice question 50 from the 2023 Gce Model Questions Vol1 Biology examination.

Gce Model Questions Vol1 2023 Biology Objective / Multiple Choice Hard Difficulty
Question 50 GCE_MODEL_QUESTIONS_VOL1 • 2023 • BIOLOGY • objective

Mountain goats live at an altitude of 3000 m where the atmospheric pressure is 70 kPa (sea‑level pressure ≈101 kPa). The fraction of oxygen in air is 0.21, so the ambient PO₂ is 0.21 × 70 = 14.7 kPa. Their haemoglobin has a P₅₀ of 3.5 kPa and a Hill coefficient n = 2.8. (a) Using the Hill equation \(S_{aO₂}=\dfrac{PO₂^{n}}{P_{50}^{n}+PO₂^{n}}\), calculate the arterial oxygen saturation (SₐO₂) at this altitude. (b) Oxygen content of blood is given by \(C_{aO₂}=Hb\times1.34\times S_{aO₂}+0.003\times PO₂\) (units: mL O₂ L⁻¹). If the goats increase their haemoglobin concentration from 150 g L⁻¹ to 180 g L⁻¹, compute the change in CₐO₂ and state whether this physiological adaptation fully compensates for the reduced PO₂ compared with sea‑level conditions (where PO₂≈21 kPa and Hb=150 g L⁻¹).

Answer Options

A. SₐO₂ ≈ 92 %; CₐO₂ rises from ~180 mL O₂ L⁻¹ to ~225 mL O₂ L⁻¹ (≈+45 mL O₂ L⁻¹), overcompensating for the lower PO₂.
B. SₐO₂ ≈ 75 %; CₐO₂ rises from ~150 mL O₂ L⁻¹ to ~190 mL O₂ L⁻¹ (≈+40 mL O₂ L⁻¹), insufficient to compensate for the lower PO₂.
Correct Answer C. SₐO₂ ≈ 98 %; CₐO₂ rises from ~198 mL O₂ L⁻¹ to ~237 mL O₂ L⁻¹ (≈+39.5 mL O₂ L⁻¹), fully compensating for the lower PO₂.
D. SₐO₂ ≈ 85 %; CₐO₂ rises from ~170 mL O₂ L⁻¹ to ~210 mL O₂ L⁻¹ (≈+40 mL O₂ L⁻¹), partially compensating for the lower PO₂.
Correct Answer
C
Correct Option:
SₐO₂ ≈ 98 %; CₐO₂ rises from ~198 mL O₂ L⁻¹ to ~237 mL O₂ L⁻¹ (≈+39.5 mL O₂ L⁻¹), fully compensating for the lower PO₂.

About This Question

This is Gce Model Questions Vol1 2023 Biology Question 50. It is one of the objective questions from the 2023 Gce Model Questions Vol1 Biology examination.

Difficulty level: Hard .

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