AQA · A-Level · Physical Education
Course version: 7582 · Version from Sept 2016
Cardiovascular system: Haemoglobin.
Haemoglobin is the iron-containing protein inside red blood cells that binds oxygen reversibly.
Checked against the AQA 7582 specification (opens in a new tab) on .
- Point 13 of 25
- 4 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
Haemoglobin is the iron-containing protein inside red blood cells that binds oxygen reversibly. Each haemoglobin molecule can bind up to four oxygen molecules, forming oxyhaemoglobin. Binding depends on the partial pressure of oxygen: at the lungs the partial pressure is high, so oxygen loads onto haemoglobin; at respiring tissues the partial pressure is lower, so oxyhaemoglobin dissociates and oxygen is released. This reversible association allows blood to pick up oxygen in the lungs and deliver it where it is needed. During exercise, increased carbon dioxide and acidity in active muscle further reduce haemoglobin's affinity for oxygen, so more oxygen is unloaded to the working tissues.
What earns the marks
- Haemoglobin is an iron-containing protein found in red blood cells that binds oxygen reversibly.
- Each haemoglobin molecule can bind up to four oxygen molecules, forming oxyhaemoglobin.
- Oxygen binds to haemoglobin at the lungs where the partial pressure of oxygen is high.
- Oxyhaemoglobin dissociates at respiring tissues where the partial pressure of oxygen is lower, releasing oxygen.
- Increased carbon dioxide and acidity in active muscle reduce haemoglobin's affinity for oxygen, increasing oxygen unloading during exercise.
- The reversible binding of oxygen allows haemoglobin to transport oxygen from the lungs to the tissues.
Common mistakes and how to put them right
Thinking haemoglobin is found in plasma.
Put it right: Haemoglobin is contained within red blood cells.
Believing haemoglobin binds oxygen irreversibly.
Put it right: The binding is reversible, which allows oxygen to be released at the tissues.
Stating that each haemoglobin molecule binds one oxygen molecule.
Put it right: It can bind up to four oxygen molecules.
Assuming haemoglobin releases oxygen at the lungs.
Put it right: It loads oxygen at the lungs and releases it at respiring tissues.
Exam tips
- Use the terms loading and dissociation to describe oxygen binding at the lungs and release at the tissues.
- Refer to the partial pressure of oxygen when explaining why haemoglobin binds or releases oxygen.
- Link reduced haemoglobin affinity in active muscle to increased carbon dioxide and acidity when explaining oxygen unloading during exercise.
Try the lesson
The start of the Cardiovascular system: Haemoglobin. lesson, made from checked teaching notes for this specification point.
Have a go first
Which metal ion is bound at the centre of each haem group within a haemoglobin molecule?
Listen
Haemoglobin is the iron-containing protein inside red blood cells that binds oxygen reversibly. Each haemoglobin molecule can bind up to four oxygen molecules, forming oxyhaemoglobin. Binding depends on the partial pressure of oxygen: at the lungs the partial pressure is high, so oxygen loads onto haemoglobin; at respiring tissues the partial pressure is lower, so oxyhaemoglobin dissociates and oxygen is released. This reversible association allows blood to pick up oxygen in the lungs and deliver it where it is needed. During exercise, increased carbon dioxide and acidity in active muscle further reduce haemoglobin's affinity for oxygen, so more oxygen is unloaded to the working tissues. A strong answer earns marks for these points. Haemoglobin is an iron-containing protein found in red blood cells that binds oxygen reversibly. Each haemoglobin molecule can bind up to four oxygen molecules, forming oxyhaemoglobin. Oxygen binds to haemoglobin at the lungs where the partial pressure of oxygen is high. Oxyhaemoglobin dissociates at respiring tissues where the partial pressure of oxygen is lower, releasing oxygen. Exam tip: Use the terms loading and dissociation to describe oxygen binding at the lungs and release at the tissues.
See it
Key words
Say what each word means before you turn the card.
Reversible oxygen binding
Try answering aloud or in your head before turning the card.
Oxyhaemoglobin formation and dissociation
Try answering aloud or in your head before turning the card.
Partial pressure of oxygen
Try answering aloud or in your head before turning the card.
Exercise and oxygen unloading
Try answering aloud or in your head before turning the card.
See every definition
- Reversible oxygen binding
- The iron-containing protein inside red blood cells binds oxygen in a way that allows oxygen to be released at the tissues.
- Oxyhaemoglobin formation and dissociation
- Each haemoglobin molecule can bind up to four oxygen molecules, forming oxyhaemoglobin, which dissociates at respiring tissues to release oxygen.
- Partial pressure of oxygen
- At the lungs this is high, so oxygen loads onto haemoglobin, while at respiring tissues it is lower, so oxyhaemoglobin dissociates and oxygen is released.
- Exercise and oxygen unloading
- During exercise, increased carbon dioxide and acidity in active muscle further reduce haemoglobin's affinity for oxygen, so more oxygen is unloaded to the working tissues.
Label the diagram
Some boxes have lost their names. Pick the right name for each number.
1Box 1
2Box 2
3Box 3
There is more to this lesson
The full lesson goes on to check your understanding and help you earn the marks. Create a free account to carry on, with your progress saved.
A week of Premium from your first lesson · Then the free plan continues · No card, no charge
Test your understanding of Cardiovascular system: Haemoglobin.
Active recall beats re-reading. Take an instant quiz now to test what you’ve learned and lock it into long-term memory.
A week of Premium from your first lesson · Then the free plan continues · No card, no charge