Oxyhemoglobin Curve Workbook

Haemoglobin and oxygen dissociation curves

Inside this booklet you will find information about haemoglobin and oxygen dissociation curves, together with an assortment of questions on the topic.

Haemoglobin and Oxygen Dissociation Curves

Haemoglobin is a protein that carries oxygen around the body.

Different species have different forms of haemoglobin, depending on where each species lives, and within a species there may be more than one version of the molecule.

Haemoglobin is found in all vertebrates as well as earthworms, starfish, some insects, some plants and even some bacteria. The red colour of haemoglobin comes from its iron content. Lobsters use a different oxygen carrying pigment called hemocyanin which uses copper instead of iron which gives them a blue colour, turning red when boiled as the copper oxidises!

Haemoglobin is a quaternary protein made of 4 polypeptide chains, each chain containing iron. The molecule has a high affinity for oxygen (this means it likes to combine with oxygen molecules), and each molecule can carry 4 oxygen molecules:

Hb + 4O2 = HbO8

Haemoglobin + oxygen = oxyhaemoglobin

This is a reversible reaction. Oxyhaemoglobin is formed in the lungs, then when oxygen dissociates (leaves) haemoglobin in the body tissues it turns back to haemoglobin.

Partial Pressure of O2: The partial pressure of oxygen (pO2) is a measure of oxygen concentration. pO2 will be high in the lungs, and lower in body tissues such as muscle.

Haemoglobin's affinity for oxygen depends on the pO2. Oxygen combines with haemoglobin to for oxyhaemoglobin where there's a high pO2, and oxyhaemoglobin breaks down to haemoglobin and oxygen where there's a lower pO2.

This means haemoglobin picks up oxygen in the lungs (high pO2) and delivers oxygen to respiring tissues where pO2 is lower as cells use up oxygen.

QUESTIONS

1. Haemoglobin is a protein with a quaternary structure. Explain what this means.

2. How many oxygen molecules can each molecule...