IB Biology HL B3.1.13 Hl Oxygen Dissociation Curves Questions

Explore how haemoglobin saturation changes with oxygen partial pressure and why dissociation-curve shape and position matter for oxygen transport in IB Biology HL B3.1.13.

Exam points

Read curve axes and use pO₂ to find haemoglobin saturation, including plateau values.
Explain how cooperative oxygen binding between haemoglobin subunits produces a sigmoid curve.
Compare adult, foetal and myoglobin curves to infer affinity and oxygen loading or tissue release.

[Maximum number: 3]

Oxygen dissociation curves show the percentage of oxygen saturation of adult haemoglobin (Hb) at different oxygen concentrations, as measured in partial pressure of oxygen ( $\mathrm{pO}_{2}$ ).

Figure for Question IB Biology HL B3.1.13 Hl Oxygen Dissociation Curves Questions question 1 — IB Biology HL

(a)

Identify the percentage of oxygen saturation of haemoglobin at a partial pressure of 40 mmHg .

[ 1 ]

(b)

Describe the relationship between partial pressure of oxygen ( $\mathrm{pO}_{2}$ ) and percent saturation of haemoglobin.

[ 2 ]

a. as $\mathrm{pO}_{2}$ increases, \% saturation increases

OR

positive correlation/relationship;

b. \% saturation levels off/plateaus/OWTTE (at higher partial pressure);

c. sigmoidal relationship/S curve;

a., b. Accept quoting values for increase and levelling off.

c. Do not accept other terms than sigmoid or S shaped curve.

Marking guidance:

Do not accept 100\% saturation.

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IB Biology HL B3.1.13 Hl Oxygen Dissociation Curves Questions question 1

Question (a)

Question (b)