7.1) Haemoglobin Flashcards
What are the haemoglobins?
The haemoglobins are a group of chemically similar molecules
What is a haemoglobin?
A protein found in red blood cells that has a quaternary structure and is specialised to carry oxygen to the tissues.
What is the primary structure of a haemoglobin molecule?
The sequence of amino acids in the four polypeptide chains
What the secondary structure of a haemoglobin molecule?
Each of the polypeptide chains are folded into a helix
What is the tertiary structure of a haemoglobin molecule?
Each polypeptide chain is folded into a specific shape
What is the quaternary structure of a haemoglobin molecule?
All 4 polypeptide chains are linked together to form a spherical molecule
What is the quaternary structure of haemoglobin?
Haemoglobin has a quaternary structure of 4 polypeptide chains
What is each polypeptide chain associated with?
A haem group that contains an Fe²⁺ (ferrous) ion
How many oxygen molecules can each haemoglobin molecule carry?
Each Fe²⁺ can bind to 1 O₂ molecule, so 1 haemoglobin molecule can carry up to 4 O₂ molecules.
What is meant by the term ‘Loading’ or ‘Associating’?
The process by which haemoglobin binds to oxygen
Where does ‘Loading’ or ‘Associating’ occur in humans?
In the lungs
What is meant by the term ‘Unloading’ or ‘Disassociating’?
The process by which haemoglobin releases its oxygen
Where does ‘Unloading’ or ‘Disassociating’ occur in humans?
In the tissues
What happens when haemoglobin has a high affinity for oxygen?
- Haemoglobin with high affinity for oxygen takes up oxygen easily.
- However, it releases oxygen less easily.
What happens when haemoglobin has a low affinity for oxygen?
- Haemoglobin with low affinity for oxygen takes up oxygen less easily.
- However, it releases oxygen more easily.
What is the role of haemoglobin in the body?
Haemoglobin’s primary role is to transport oxygen.
To be efficient, it must:
- Associate with oxygen at gas exchange surfaces (e.g., lungs).
- Dissociate from oxygen at tissues requiring it (e.g., respiring tissues).
How does haemoglobin change its affinity for oxygen?
Haemoglobin changes shape in response to carbon dioxide.
More CO₂ → Lower affinity → Releases oxygen.
Less CO₂ → Higher affinity → Binds oxygen.
What happens to haemoglobin at the gas exchange surface (e.g., lungs)?
- High oxygen concentration ~ Low carbon dioxide concentration
- High affinity for oxygen.
- Oxygen is associated with haemoglobin (picked up).
What happens to haemoglobin at respiring tissues (e.g., muscles)?
- Low oxygen concentration ~ High carbon dioxide concentration
- Low affinity for oxygen
- Oxygen is dissociated from haemoglobin (released).
Why does haemoglobin release oxygen in tissues with high carbon dioxide concentration?
- High carbon dioxide changes haemoglobin’s shape.
- This lowers its affinity for oxygen.
- Haemoglobin release oxygen where it’s needed.
What is the primary function of haemoglobin?
Haemoglobin carries oxygen from the gas-exchange surface to tissues that require it for respiration.
Why did scientists investigate haemoglobin in different organisms?
To study its ability to combine with oxygen and understand differences in how organisms take up and release oxygen.
What did scientists discover about different haemoglobins?
Different haemoglobins exhibit distinct properties related to oxygen uptake and release.
Why do different haemoglobins have varying affinities for oxygen?
There are differences in their amino acid sequences, which affect their tertiary and quaternary structures and oxygen-binding properties.
How does the shape of haemoglobin molecules affect their function?
The shape determines their affinity for oxygen, ranging from high to low oxygen-binding capabilities.
What structural differences exist between haemoglobins of different species?
Each species’ haemoglobin has a slightly different amino acid sequence, altering its tertiary and quaternary structure.
PQ:
What is the quaternary structure of haemoglobin?
Haemoglobin has a quaternary structure made up of four polypeptide chains, each containing a haem group that binds oxygen.
PQ:
How does DNA lead to different haemoglobin molecules having different affinities for oxygen?
DNA determines the amino acid sequence of haemoglobin, which affects its tertiary and quaternary structure, leading to variations in oxygen-binding affinity.
PQ:
Why is it beneficial that, at rest, only one oxygen molecule is released from haemoglobin into the tissues?
This ensures a reserve of oxygen remains bound to haemoglobin, which can be released when the organism becomes more active and requires more oxygen.
PQ:
Why might a person breathing in car-exhaust fumes lose consciousness?
Carbon monoxide binds permanently to haemoglobin, preventing oxygen transport, leading to hypoxia and loss of consciousness.
