IB Biology HL B3.1.13 Hl Oxygen Dissociation Curves Questions

Explore how oxygen partial pressure determines haemoglobin saturation, why cooperative binding creates a sigmoid curve and how curve position predicts affinity and tissue oxygen delivery in IB Biology HL B3.1.13.

Exam points

Read oxygen dissociation curves by identifying percentage haemoglobin saturation on the y-axis and oxygen partial pressure on the x-axis, including values and plateau regions.
Explain the sigmoid curve as evidence of cooperative oxygen binding between haemoglobin subunits.
Compare curve positions for adult, fetal haemoglobin and myoglobin to infer relative oxygen affinity and consequences for loading in lungs or unloading in 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 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.

2
max

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

Question (a)

Question (b)