Oxygen and the Bohr Effect Flashcards
How is oxygen carried?
By combining loosely with haemoglobin in red blood cells.
Outline how oxygen is loaded and unloaded
Blood enters the lung capillaries deoxygenated. Alveoli have a [high] of oxygen, giving a gradient for oxygen diffusion through the wall of the alveolus and capillary. Oxyhaemoglobin is formed, and oxygen is carried away by the blood, maintaining a [gradient]. Oxyhaemoglobin releases oxygen to respiring cells.
What is the oxygen haemoglobin dissociation curve?
A graph that shows the relationship between the amount of oxygen carried by haemoglobin and the partial pressure of oxygen in the surrounding environment.
Why is there a curve in the OHDC? Why is it so shallow initially?
When haemoglobin is exposed to different partial pressures of oxygen, it doesn’t absorb it evenly. The gradient of the curve is shallow at first because the shape of the haemoglobin makes it difficult for the first oxygen molecules to bind as they’re closely united.
Why is haemoglobin suited as a respiratory pigment for the transport of oxygen from the lungs?
It has a high affinity for oxygen and quickly associated with oxygen (96% saturated) in the lungs where PPO is high. At low PPO, haemoglobin dissociates some O2 to the respiring cells. The release is increased due to high {CO2} in cells.
What does the first oxygen molecule do to the haemoglobin?
It changes the quaternary structure, making it easier for other subunits to bind to the O2 molecule.
What is positive cooperativity?
The binding of the first molecule making the following binding easier. It takes a smaller increase in the PPO to bind to the second oxygen molecule than it did to bind to the 1st one. This makes the gradient of the curve steepen.
Why is it harder for the 4th molecule to bind?
Almost all the sites are occupied, so the probability is low. The gradient of the curve reduces and the graph flattens off.
What is the Bohr Effect? When does it occur and why?
The Bohr effect is when the O2 dissociation curve moves to the right as CO2 depresses it, and haemoglobin releases more oxygen to respiring tissues. It occurs during vigorous exercise due to the decrease in pH produced as carbon dioxide dissolves in blood plasma to form an acid.
What is the effect of temperature on the dissociation curve?
Increase in temperature depresses the curve too, more O2 is released to cells and more heat is released when respiration increases.
