Haemoglobin and Dissociation Flashcards
What is haemoglobin and where is it found?
- Found in red blood cells
- Made up of 4 polypeptide chains, each with a haem group
- Iron ion gives haemoglobin its red colour
- Haemoglobin has a high affinity for oxygen- binds to oxygen molecules strongly
- Oxygen joins to haemoglobin to form oxyhemoglobin
- Oxyhemoglobin can unload and dissociate- allows oxygen to diffuse into body cells for respiration
What is the partial pressure of oxygen?
Concentration of dissolved oxygen in cells
What does haemoglobin’s affinity for oxygen depend on?
The environment
What happens when the partial pressure of oxygen increases?
- Affinity to oxygen increases
- Haemoglobin loads oxygen more readily than it unloads and dissociates.
- More saturated with oxygen
What happens when the partial pressure of oxygen decreases?
- Affinity to oxygen decreases
- Haemoglobin unloads and dissociates oxygen more readily than it loads
- Less saturated with oxygen
What does % saturation of haemoglobin represent?
Number of oxygen molecules bound to haemoglobin
What happens to haemoglobin in the lungs?
- Alveoli in the lungs have a high pO₂
- Haemoglobin’s affinity for oxygen increases
- Haemoglobin readily loads oxygen- higher saturation
What happens to haemoglobin at body cells?
- Red blood cells deliver oxyhemoglobin to respiring tissues- use up oxygen
- These tissues have a low pO₂
- Affinity for oxygen decreases
- Readily unloads and dissociates oxygen
- Decreased saturation
How is haemoglobin different in different organisms?
- Due to variations in amino acid sequences
- Help them survive in specific environments
How is haemoglobin adapted in organisms that live in low oxygen environments?
- High affinity for oxygen
- Loads oxygen more readily at a lower partial pressure
- Unloads less readily- higher saturation
- Dissociation curve is shifted to the left
Eg. Llamas living at high altitudes where pO₂ is low.
How is haemoglobin adapted in highly active animals?
- Low affinity for oxygen
- It unloads oxygen more readily for respiration
- Dissociation curve is shifted to the right
Eg. Cheetahs, which require a high oxygen supply
What is the Bohr effect?
- As the partial pressure of CO₂ increase
Haemoglobin’s affinity for oxygen decreases - Unloads and dissociates oxygen more readily than it loads
- Percentage of oxygen saturation decreases
- More oxygen released - more aerobic respiration
- Dissociation curve shifts to the right
What causes the Bohr effect?
- CO₂ from respiring cells diffuses into red blood cells
- CO₂ reacts with water in plasma to form carbonic acid
- Carbonic acid dissociates into H⁺ ions and hydrogencarbonate
- Increase in H⁺ ions causes oxyhaemoglobin to unload oxygen
- Haemoglobin takes up H⁺ ions to form haemoglobinic acid- prevents a drop in pH
- Hydrogencarbonate ions diffuse out of red blood cells into plasma
- Chloride ions enter red blood cells to maintain electrochemical balance
How does haemoglobin regain its oxygen-binding ability in the lungs?
- High partial pressure of oxygen in the lungs causes haemoglobic acid to dissociate
- H⁺ ions bind with hydrogencarbonate ions- form carbonic acid
- Carbonic acid is broken down into carbon dioxide and water
- Carbon dioxide is exhaled freeing haemoglobin to bind oxygen again
How does fetal haemoglobin differ from adult haemoglobin?
- Has higher affinity for oxygen than adult haemoglobin
- Fetal haemoglobin binds oxygen more readily than adult haemoglobin
- Placenta has a low partial pressure of oxygen
- Adult haemoglobin unloads oxygen- diffuses into fetal haemoglobin
Fetal haemoglobin loads oxygen at this low partial pressure- more saturated
Why is it necessary for fetal haemoglobin to have a higher oxygen affinity?
- Ensures that the fetus receives sufficient oxygen for respiration
- Oxygen is needed for energy production to support high metabolic demand (e.g., rapid cell division and growth)
What is myoglobin and its function?
- Dark red pigment found in muscle cells
- Doesn’t transport O₂ but stores it
- High affinity for O₂
- It picks up O₂ readily and only releases it when levels drop very low
- Myoglobin releases O₂ when needed in very active muscles
- Muscles switch to anaerobic respiration if O₂ levels drop too low
How does body size affect haemoglobin affinity?
- Small mammals have a higher SA:V- lose heat quickly
- High metabolic rate to maintain body temperature
- O₂ demand is high- haemoglobin has lower affinity
- Dissociation curve shifts to the right
