oxidation curve

describe haemoglobin

Haemoglobin is made up of 2 different types of subunits A and B there are 2 of each of these types so in total 4. Each subunit has the prosthetic group haem attached. Within the haem group there is the Fe2+ ion which oxygen can bind to

what is the equation for oxygen binding (loading) and unbinding (unloading)

Hb+4O2=Hb(O2)4 this is a reversible reaction

what does affinity mean

How strongly the oxygen is bound the haemoglobin

what is this called

What is the partial pressure

what is this type of curve called

oxygen dissociation curve

basically the concentration of oxygen

sigmodal

describe what happens in the graph

As we increase the partial pressure of oxygen the percentage saturation increases very slowly at around 4KPa the rate of saturation begins to increase. The haemoglobin is 25% saturated. At around 7 KPa and 75% saturation (2 oxygen molecules have joined) the rate of saturating begins to slow.

Explain the oxygen dissociation curve

1. Its hard for the first oxygen molecules to bind to one of the four sites on haemoglobin because the polypeptide subunits are closely held together so its hard for the oxygen molecule to access the Fe2+ ion. Therefore at a low practical pressure little oxygen binds to haemoglobin so the curve is shallow.

2. Once an oxygen binds to the haemoglobin it changes the quaternary structure of the haemoglobin. the globin chains open up so that the second and third oxygen molecules can bind easier to Fe2+ ions. Only a small increase in partial pressure causes lots more oxygen to bind

3. Due to the haemoglobin being almost fully saturated (there are less spaces for O2 to collide with and bind) Its harder for it to bind to an Fe2+ ion. This cause the gradient of the curve to decrease and plateaus. When the partial pressure of oxygen is lower than the atmospheric pressure of 21KPa haemoglobin is normally fully saturated

There abouts is the blood when its at its highest percentage saturation

alveoli

where is the blood going to as this saturation drops

tissue

what is a factor that effects the graph

carbon dioxide

Describe the difference between low and high level of CO2 and what that mean for the affinity of oxygen

high levels of CO2 cause the oxygen dissociation curve to shift the right. CO2 causes the oxygen affinity of haemoglobin to decrease. So its easier to loose the oxygen

what is the shift right called

Bohr effect

How does CO2 cause the structure of the haemoglobin to change

In the blood carbon dioxide can firm the acidic molecule carbonic acid. This releases the hydrogen ion H+. This H+ combines with the haemoglobin and causes it to change its quaternary structure. This results in haemoglobin having a lower affinity for oxygen.