Structure of haemoglobin and dissociation curve Flashcards
What is the function of a red blood cell?
RBC contain hb so can transport O2 in the blood
-Describe the structure of the protein haemoglobin?
Hb are groups of proteins found in different organisms. Hb has a 4ternary structure Hb and RBC in charge of transport of oxygen. e.g Myoglobin stores O2 and hold even in low partial pressures. Found in muscles tissue in vertebrates.
What does the “Affinity of haemoglobin for oxygen” mean?
Ability of Hb to bind O2 to it
What does “Saturation of haemoglobin with oxygen” mean?
When Hb holds max amount of O2 it can bind
-What does “Loading/association of haemoglobin” mean?
When O2 binds to Hb
-What does “unloading/dissociation of haemoglobin” mean?
When the O2 detaches from the Hb.
-What does partial pressure mean?
Concentration of Hb
-So what’s happening during a Dissociation curve
Curve is described as a sigmoid curve and demonstrates that when O2 is loaded at regions with a high partial pressure of oxygen (like alveoli) , it is at almost 100% saturation. AT higher pp, then will have a higher affinity for O2 so will load more O2 so when its transported in RBC it can be unloaded at low respiring tissues. At low pp, its only abt 50% saturation. When you have a lower PP, Hb doesn’t have a high affinity for O2 so won’t attract 02 well so will unload o2 in those regions (like respiring tissues).
-How does Cooperative binding explain the rapid curve of the dissociation curve?
The cooperative binding nature of oxygen binding to haemoglobin is due to the haemoglobin changing shape when the first oxygen binds. This makes it easier for further oxygen to bind therefore the graph curves up rapidly.
-How does Different conditions affect haemoglobin’s affinity? -THE BOHR EFFECT. What is it?
The Bohr effect is when HIGH CO2 concentration causes the OXYHAEMOGLOBIN curve to shift to the RIGHT. The affinity of oxygen decreases because the acidic carbon dioxide CHANGES the SHAPE of HAEMOGLOBIN slightly. The CO2 forms CARBONIC ACID when it dissolves in the water in the blood, so LOTS OF RESPIRATION then LOTS OF CO2 DISSOLVE so BLOOD becomes ACIDIC and curve of graph shifts to RIGHT. This means that Hb AFFINITY for O2 has DECREASED so will more READILY UNLOAD oxygen.
Example of comparisons in Bohr graph pH 7.6 VS 7.2
pH 7.6: Low Pp of Co2 in the alveoli. Curve shifts left, increased affinity therefore uploads more oxygen. pH 7.2: High PP of CO2 at respiring tissues. Dissolves into blood so more acidic so shape of Hb changes slightly so affinity decreases so unloads O2 more readily.
Why is the Bohr effect advantageous?
Even at same PP of 02, if have more CO2 present the affinity decreases (see through lower saturation of O2). Whereas, if you don’t have a lot of CO2 then there’s a higher affinity (so higher saturation of O2) which is advantageous. Unloading max at respiring tissues and loading at areas of high saturation of O2 so max ATP made so muscle contraction.
Animals have different affinities for O2 which are adapted to their different environments.. Examples:
Foetuses have a higher affinity for oxygen. Good coz only source of O2 is from mother’s Hb in placenta so needs higher affinity so can get enough O2. Lamas have high affinity for o2 coz live in areas of high altitudes. Dove shifts to right so low affinity for 02. Have faster metabolisms so need more O2 for respiration to provide enough energy for contracting muscles. NEED HIGHER SUPPLY. Low affinity so more readily unloaded.
-How do you tell in comparison dissociation curves if an animal ect has a higher or lower affinity for O2 compared to the other subject?
Look at whether the curve shifts LEFT or RIGHT in comparison to human. Left- higher affinity coz at same PP its more saturated in O2 Right- lower affinity coz at same PP its less saturated in o2 so must be unloading.
