Section 3- Haemoglobin Flashcards
What is the structure of haemoglobin?
Globular protein with a quaternary structure
(4 polypeptide chains)
4 chains= 2 alpha chains, 2 beta chains
What part of the haemoglobin binds to an oxygen molecule?
The prosthetic group- contains a iron ion
What is created when oxygen binds to haemoglobin?
Oxyhaemoglobin (HbO8)
Why is oxygen binding and unbinding a reversible reaction?
Oxygen is LOADED in the lungs and UNLOADED in the tissues
What is the process by which haemoglobin bind and unbinding with oxygen is called?
Loading or associating
Unloading or dissociating
What is cooperative binding?
When a molecule of oxygen binds to haemoglobin, it changes the tertiary structure slightly revealing other binding sites
Haemoglobins with a high affinity for oxygen…
take up oxygen more easily, but release it less easily
Haemoglobins with a low affinity for oxygen…
take up oxygen less easily, but release it more easily
What is the affinity for oxygen affected by?
The partial pressure of oxygen in the tissues surrounding the haemoglobin
What is the role of haemoglobin?
Transport oxygen
To be efficient at transporting oxygen, haemoglobin must…
- readily associate with oxygen at the surface where gas exchange takes place
- readily dissociate from oxygen at tissues requiring it
How does DNA lead to different haemoglobin molecules having different affinities for oxygen?
Different base sequence
Different amino acid sequence
Different tertiary and quaternary structure and shape
Different affinities for oxygen
Why might a person breathing in car-exhaust fumes lose consciousness?
(When carbon monoxide binds permanently to haemoglobin in preference to oxygen)
Carbon monoxide will occupy all site of haemoglobin instead of oxygen
No oxygen will be carried to tissues (brain)
Cease to respire and to function
Person loses consciousness
What shape is an oxygen dissociation graph?
S (sigmoid shape)
In the lungs where the partial pressure of oxygen is high…
Haemoglobin has a high affinity
Loads or associates with lots of oxygen
In the tissues with a low respiration rate, the partial pressure of oxygen…
Is relatively low
The affinity for oxygen decreases
In tissues with a high respiration rate, the partial pressure of oxygen is…
Much lower
How does the partial pressure of carbon dioxide affect oxygen-haemoglobin binding?
As partial pressure of CO2 increases, conditions are more acidic- haemoglobin changes shape.
The affinity of haemoglobin for oxygen decreases
Oxygen is released from haemoglobin
THE BOHR EFFECT
How does partial pressure of oxygen affect oxygen-haemoglobin binding?
As partial pressure of oxygen increases, the affinity of haemoglobin for oxygen increases
Oxygen binds tightly to haemoglobin
When partial pressure is low, oxygen is released from haemoglobin
What acid is produced when CO2 dissolves into blood plasma and reacts with water?
Carbonic acid
Why does the oxygen dissociation curve steeply increase?
The 2nd and 3rd oxygen molecules bind easily to the haemoglobin.
How is the affinity for oxygen affected when the oxygen dissociation curve is further to the left?
Greater affinity of haemoglobin for oxygen
Loads oxygen readily but unloads less easily
What is the Bohr effect?
The greater the concentration of carbon dioxide, the more readily the haemoglobin releases it oxygen
When a tissue is more active, more oxygen is unloaded. Why?
Higher rate of respiration More carbon dioxide is produced by tissues Lower pH Greater haemoglobin shape change More readily oxygen is unloaded More oxygen is available for respiration
What effect does a change in tertiary structure have with oxygen affinity?
Affinity for oxygen will be lower
More oxygen is unloaded
How has haemoglobin adapted in low oxygen environments?
Haemoglobin becomes fully saturated at lower partial pressure of oxygen
Higher affinity for oxygen
Fully saturated at much lower partial pressure of oxygen
How has haemoglobin adapted with highly active animals?
Haemoglobin has a lower affinity for oxygen
Unloads much quicker to respiring tissues
Decrease in partial pressure
More oxygen to respiring tissues
How has haemoglobin adapted in animals with a large surface area to volume ratio?
High metabolic rate, requires more oxygen
Higher partial pressure
Respiring tissues get more oxygen
How does a rise in temperature enable an exercising muscle to work more efficiently?
Exercising muscles release heat
Shifts curve to the right
Haemoglobin releases more oxygen to fuel muscular activity
How do you calculate percentage saturation of haemoglobin with oxygen?
(Oxygenated Hb / Maximum saturation) X 100
What enzyme catalyses the reaction where carbon dioxide diffuses diffuses into the red blood cells?
Carbonic anhydrase
What is the advantage of foetal haemoglobin having a different dissociation curve from maternal haemoglobin?
Higher affinity at lower partial pressure.
Able to become fully saturated with oxygen from mothers blood.
Foetus has high respiration so needs lots of oxygen.
When hydrogen ions combine with haemoglobin, they form a compound known as…
haemoglobinic acid
What enzyme catalyses the reaction leading to the production of hydrogen ions and hydrogen carbonate ions after the diffusing of CO2 into the red blood cells?
Carbonic anhydrase
