Haemoglobin A* notes Flashcards
(13 cards)
Describe the role of red blood cells & haemoglobin (Hb) in oxygen transport
● Red blood cells contain lots of Hb
○ No nucleus & biconcave → more space for Hb, high SA:V & short diffusion distance
● Hb associates with / binds / loads oxygenat gas exchange surfaces (lungs) where partial
pressure of oxygen (pO2) is high
● This forms oxyhaemoglobin which transports oxygen
○ Each can carry four oxygen molecule, one at each Haem group
● Hb dissociates from / unloads oxygen near cells / tissues where pO2
is low
Describe the structure of haemoglobin
● Protein with a quaternary structure
● Made of 4 polypeptide chains
● Each chain contains a Haem group containing an iron ion (Fe
2+)
Describe the loading, transport and unloading of oxygen in relation to the
oxyhaemoglobin dissociation curve
Areas with low pO2 - respiring tissues
● Hb has a low affinity for oxygen
● So oxygenreadily unloads / dissociates with Hb
● So % saturation is low
Areas with high pO2 - gas exchange surfaces
● Hb has a high affinity for oxygen
● So oxygenreadily loads / associates with Hb
● So % saturation is high
Explain how the cooperative nature of oxygen binding results in an S-shaped (sigmoid) oxyhaemoglobin dissociation curve
- Binding of first oxygen changes tertiary / quaternary structure of haemoglobin
- This uncovers Haem group binding sites, making further binding of oxygens easier
Describe evidence for the cooperative nature of oxygen binding
● A low pO2 as oxygen increases there is little / slow increase in % saturation of Hb with oxygen
○ When first oxygen is binding
● At higher pO2
, as oxygen increases there is a big / rapid increase in % saturation of Hb with oxygen
○ Showing it has got easier for oxygens to bind
What is the Bohr effect?
Effect of CO2 concentration on dissociation of oxyhaemoglobin → curve shifts to right
Explain effect of CO2 concentration on the dissociation of oxyhaemoglobin
- Increasing blood CO2 eg. due to increased rate of respiration
- Lowers blood pH (more acidic)
- Reducing Hb’s affinity for oxygen as shape / tertiary / quaternary structure changes slightly
- So more / faster unloading of oxygen to respiring cells at a given pO2
Describe evidence for the Bohr effect
At a given pO2 %, the saturation of Hb with oxygen is lower
Explain the advantage of the Bohr effect (eg. during exercise)
More dissociation of oxygen → faster aerobic respiration / less anaerobic respiration → more ATP produced
Explain why different types of haemoglobin can have different oxygen transport properties
● Different types of Hb are made of polypeptide chains with slightly different amino acid sequences
● Resulting in different tertiary / quaternary structures / shape
● So they have different affinities for oxygen
Explain how organisms can be adapted to their environment by having
different types of haemoglobin with different oxygen transport properties
Curve shift left-Hb has higher affinity for O2
● More O2 associates with Hb more readily
● At gas exchange surfaces where pO2
is lower
● Eg. organisms in low O2 environments - high
altitudes, underground, or foetuses
Curve shift right-Hb has lower affinity for O2
● More O2 dissociates from Hb more readily
● At respiring tissues where more O2
is needed
● Eg. organisms with high rates of respiration /
metabolic rate (may be small or active)
Describe the general pattern of blood circulation in a mammal
Closed double circulatory system - blood passes through heart twice for every circuit around body:
1. Deoxygenated blood in right side of heart pumped to lungs; oxygenated returns to left side
2. Oxygenated blood in left side of heart pumped to rest of body; deoxygenated returns to right
Suggest the importance of a double circulatory system
● Prevents mixing of oxygenated / deoxygenated blood
○ So blood pumped to body is fully saturated with oxygen for aerobic respiration
● Blood can be pumped to body at a higher pressure (after being lower from lungs)
○ Substances taken to / removed from body cells quicker / more efficiently
