8.2.1
Haemoglobin
Haemoglobin
Haemoglobin
Haemoglobin is a globular protein found in red blood cells. Haemoglobin carries oxygen from the lungs around the body.


Quaternary stucture
Quaternary stucture
- Haemoglobin is a protein made from four different polypeptide chains.
- The four chains give haemoglobin a quaternary structure.


Haem groups
Haem groups
- Each polypeptide chain in a haemoglobin molecule has a haem group.
- A haem group is a prosthetic group that is attached to the protein.
- The haem groups contain an iron ion.
- The iron ion is what makes haemoglobin red.


Affinity
Affinity
- Haemoglobin has a high affinity (attraction) for oxygen.
- When red blood cells reach the lungs, oxygen diffuses into the red blood cells and binds to haemoglobin.
- Four molecules of oxygen bind to one molecule of haemoglobin.
- When oxygen binds to haemoglobin, oxyhaemoglobin is formed.


Dissociation
Dissociation
- When the red blood cells reach the tissues in the body (e.g. muscle cells), oxygen is released from the oxyhaemoglobin in a process called dissociation.
Partial Pressure
Partial Pressure
Haemoglobin has the ability to bind to oxygen and dissociate from oxygen. This is controlled by the partial pressure (concentration) of oxygen in the surrounding cells.


Partial pressure
Partial pressure
- Oxygen partial pressure (pO2) is the concentration of oxygen in the cells.
- Carbon dioxide partial pressure (pCO2) is the concentration of carbon dioxide in the cells.
- pO2 is important in determining whether oxygen binds to haemoglobin.


Affinity
Affinity
- pO2 determines the affinity of haemoglobin for oxygen.
- If pO2 is high, haemoglobin has a high affinity for oxygen and oxygen binds to haemoglobin.
- If pO2 is low, haemoglobin has a low affinity for oxygen and oxygen dissociates from haemoglobin.


Transport of oxygen
Transport of oxygen
- The effect of pO2 on the affinity of haemoglobin allows oxygen to be transported from the lungs (where there is lots of oxygen) to the respiring tissues (where oxygen is limited).
- This allows oxygen to be transported to the cells where oxygen is needed most.
Role of Haemoglobin
Role of Haemoglobin
Haemoglobin is vital for most vertebrates in carrying oxygen in the blood for respiration in the body’s cells. Haemoglobin also carries some of the carbon dioxide produced as a waste product in respiration and performs other important roles in the survival of many multicellular animals.


Reversible binding of oxygen with haemoglobin
Reversible binding of oxygen with haemoglobin
- It is important that oxygen is able to release from haemoglobin after binding as it is required in tissue cells around the body.
- 98% of haemoglobin is saturated with oxygen in lungs, whereas only 32% is saturated in respiring tissues. This illustrates how oxygen is able to dissociate from haemoglobin for use in cellular respiration.


Affinity for carbon dioxide
Affinity for carbon dioxide
- Carbon dioxide must be transported to the lungs to be breathed out as a waste product of respiration.
- Around 20% of carbon dioxide in the blood is bound to haemoglobin molecules. When carbon dioxide binds directly to haemaglobin, carbaminohaemoglobin is formed.
- But, the majority of carbon dioxide is converted to carbonic acid by carbonic anhydrase.


Carbonic anhydrase
Carbonic anhydrase
- Carbonic anhydrase is the enzyme that converts carbon dioxide into carbonic acid in the red blood cells then back to carbon dioxide when it reaches the lungs.
- Carbonic acid dissociates into bicarbonate (hydrogen carbonate) ions and hydrogen ions in the blood.
- pH is maintained by buffering agents such as haemoglobin itself that bind with the hydrogen ions to prevent a fall in pH.
- When hydrogen ions bind to haemaglobin, haemaglobinic acid is formed.
1Cell Structure
1.1Cell Structure
1.1.1Studying Cells - Microscopes
1.1.2Introduction to Eukaryotic & Prokaryotic Cells
1.1.3Ultrastructure of Eukaryotic Cells
1.1.4Ultrastructure of Eukaryotic Cells 2
1.1.5Ultrastructure of Eukaryotic Cells 3
1.1.6Prokaryotic Cells
1.1.7Viruses
1.1.8End of Topic Test - Cell Structure
1.1.9Exam-Style Question - Microscopes
1.1.10A-A* (AO2/3) - Cell Structure
2Biological Molecules
2.1Testing for Biological Modules
2.2Carbohydrates & Lipids
2.3Proteins
3Enzymes
4Cell Membranes & Transport
4.1Biological Membranes
5The Mitotic Cell Cycle
6Nucleic Acids & Protein Synthesis
6.1Nucleic Acids
7Transport in Plants
8Transport in Mammals
8.1Circulatory System
8.2Transport of Oxygen & Carbon Dioxide
9Gas Exchange
9.1Gas Exchange System
10Infectious Diseases
10.1Infectious Diseases
10.2Antibiotics
11Immunity
12Energy & Respiration (A2 Only)
13Photosynthesis (A2 Only)
14Homeostasis (A2 Only)
14.1Homeostasis
14.2The Kidney
14.3Cell Signalling
14.4Blood Glucose Concentration
14.5Homeostasis in Plants
15Control & Coordination (A2 Only)
15.1Control & Coordination in Mammals
15.1.1Neurones
15.1.2Receptors
15.1.3Taste
15.1.4Reflexes
15.1.5Action Potentials
15.1.6Saltatory Conduction
15.1.7Synapses
15.1.8Cholinergic Synnapses
15.1.9Neuromuscular Junction
15.1.10Skeletal Muscle
15.1.11Sliding Filament Theory Contraction
15.1.12Sliding Filament Theory Contraction 2
15.1.13Menstruation
15.1.14Contraceptive Pill
15.2Control & Co-Ordination in Plants
16Inherited Change (A2 Only)
16.1Passage of Information to Offspring
16.2Genes & Phenotype
17Selection & Evolution (A2 Only)
17.2Natural & Artificial Selection
18Classification & Conservation (A2 Only)
18.1Biodiversity
18.2Classification
19Genetic Technology (A2 Only)
19.1Manipulating Genomes
19.2Genetic Technology Applied to Medicine
19.3Genetically Modified Organisms in Agriculture
Jump to other topics
1Cell Structure
1.1Cell Structure
1.1.1Studying Cells - Microscopes
1.1.2Introduction to Eukaryotic & Prokaryotic Cells
1.1.3Ultrastructure of Eukaryotic Cells
1.1.4Ultrastructure of Eukaryotic Cells 2
1.1.5Ultrastructure of Eukaryotic Cells 3
1.1.6Prokaryotic Cells
1.1.7Viruses
1.1.8End of Topic Test - Cell Structure
1.1.9Exam-Style Question - Microscopes
1.1.10A-A* (AO2/3) - Cell Structure
2Biological Molecules
2.1Testing for Biological Modules
2.2Carbohydrates & Lipids
2.3Proteins
3Enzymes
4Cell Membranes & Transport
4.1Biological Membranes
5The Mitotic Cell Cycle
6Nucleic Acids & Protein Synthesis
6.1Nucleic Acids
7Transport in Plants
8Transport in Mammals
8.1Circulatory System
8.2Transport of Oxygen & Carbon Dioxide
9Gas Exchange
9.1Gas Exchange System
10Infectious Diseases
10.1Infectious Diseases
10.2Antibiotics
11Immunity
12Energy & Respiration (A2 Only)
13Photosynthesis (A2 Only)
14Homeostasis (A2 Only)
14.1Homeostasis
14.2The Kidney
14.3Cell Signalling
14.4Blood Glucose Concentration
14.5Homeostasis in Plants
15Control & Coordination (A2 Only)
15.1Control & Coordination in Mammals
15.1.1Neurones
15.1.2Receptors
15.1.3Taste
15.1.4Reflexes
15.1.5Action Potentials
15.1.6Saltatory Conduction
15.1.7Synapses
15.1.8Cholinergic Synnapses
15.1.9Neuromuscular Junction
15.1.10Skeletal Muscle
15.1.11Sliding Filament Theory Contraction
15.1.12Sliding Filament Theory Contraction 2
15.1.13Menstruation
15.1.14Contraceptive Pill
15.2Control & Co-Ordination in Plants
16Inherited Change (A2 Only)
16.1Passage of Information to Offspring
16.2Genes & Phenotype
17Selection & Evolution (A2 Only)
17.2Natural & Artificial Selection
18Classification & Conservation (A2 Only)
18.1Biodiversity
18.2Classification
19Genetic Technology (A2 Only)
19.1Manipulating Genomes
19.2Genetic Technology Applied to Medicine
19.3Genetically Modified Organisms in Agriculture
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