IB Biology HL 3.1.13 Oxygen Dissociation Curves Question Bank

Practise IB Biology HL 3.1.13 by reading sigmoid oxygen dissociation curves and comparing haemoglobin, fetal haemoglobin and myoglobin affinity.

Exam points

Read sigmoid curves to relate partial pressure of oxygen to haemoglobin saturation.
Compare adult, fetal haemoglobin and myoglobin curves using affinity and loading differences.
Use curve values to explain oxygen loading in lungs and unloading in respiring tissues.

[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 B3.1.13 (HL)—Oxygen dissociation curves 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.

2
max

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B3.1.13 (HL)—Oxygen dissociation curves question 1

Question (a)

Question (b)