What does an oxygen dissociation curve show?

The relationship between the partial pressure of oxygen and the percentage saturation of haemoglobin with oxygen.

What is the shape of the oxygen dissociation curve for haemoglobin, and why?

S-shaped (sigmoid), due to cooperative binding of oxygen.

How does the oxygen dissociation curve of fetal haemoglobin compare to that of adult haemoglobin?

Fetal haemoglobin has a higher affinity for oxygen, so its curve is shifted to the left of the adult curve.

Why is it advantageous for fetal haemoglobin to have a higher oxygen affinity than adult haemoglobin?

It allows the fetus to obtain oxygen from maternal blood across the placenta, where oxygen partial pressure is relatively low.

What is the Bohr effect?

The Bohr effect is the shift of the oxygen dissociation curve to the right at higher carbon dioxide concentrations, reducing haemoglobin's affinity for oxygen.

Explain the physiological significance of the Bohr effect.

It promotes oxygen unloading in actively respiring tissues where carbon dioxide concentration is high, ensuring oxygen is delivered where it is most needed.

OCR A-Level Biology H420

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Transport in Animals

Oxygen dissociation curves and the Bohr effect

1 thing to know
Components 01 and 03

Overview

Why the curve is sigmoid, how fetal haemoglobin differs from adult haemoglobin, and the shift the Bohr effect produces and what it achieves in respiring tissue.

What you need to know

Answer each one before you reveal it.

Your recallNot started

Process

Explain oxygen transport by haemoglobin.

Questions from this subtopic

Each one with the model answer underneath.

1
What does an oxygen dissociation curve show?
Model answer
The relationship between the partial pressure of oxygen and the percentage saturation of haemoglobin with oxygen.
2
What is the shape of the oxygen dissociation curve for haemoglobin, and why?
Model answer
S-shaped (sigmoid), due to cooperative binding of oxygen.
3
How does the oxygen dissociation curve of fetal haemoglobin compare to that of adult haemoglobin?
Model answer
Fetal haemoglobin has a higher affinity for oxygen, so its curve is shifted to the left of the adult curve.
4
Why is it advantageous for fetal haemoglobin to have a higher oxygen affinity than adult haemoglobin?
Model answer
It allows the fetus to obtain oxygen from maternal blood across the placenta, where oxygen partial pressure is relatively low.
5
What is the Bohr effect?
Model answer
The Bohr effect is the shift of the oxygen dissociation curve to the right at higher carbon dioxide concentrations, reducing haemoglobin's affinity for oxygen.
6
Explain the physiological significance of the Bohr effect.
Model answer
It promotes oxygen unloading in actively respiring tissues where carbon dioxide concentration is high, ensuring oxygen is delivered where it is most needed.

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