Rather than memorizing what does what at specific conditions, I think it's helpful to just ask yourself where you want to go. When you consider things that way, all you need to remember is the reaction itself: CO2 + H2O <=> H2CO3 <=> H+ + HCO3-
They key thing to realize is that the physiological changes that occur are in essence, Lechatlier's Principle.
Some divers exhale several times (hyperventilate) within a given period to eliminate as much CO2 as possible from our blood. This allows them to hold their breath longer in water. But what exactly is achieved by that? Well, by hyperventilating, we are releasing a lot of CO2 out of the body. In accordance with Lechatlier's Principle, the reaction above will shift to the left to make up for the CO2 lost. What's the consequence of this? Well, H+ is consumed, meaning less is present in the blood. What does this do to pH? It increases it (resulting in 'alkalosis').
Now consider what happens when TOO much CO2 is in the body -- too little breathing (hypoventilation). Our blood becomes very acidic (acidosis) and we accumulate a lot of HCO3- which must be excreted by our kidneys.
The Bohr effect essentially describes oxygen's affinity for hemoglobin in varying environments. In tissues of our body, where metabolism is readily occuring, we expect CO2 concentration to be high, pH to be low (as a direct consequence of high [CO2]), and lots of heat (high temperature). With this in mind, do you think it's best for hemoglobin to have high or low affinity for oxygen? Which is better for our tissues? Well, of course, we want CO2 to diffuse out of there as much as possible -- and because O2 is being readily consumed, we need to replenish our oxygen supply; Therefore, hemoglobin MUST have low affinity for oxygen, so that oxygen can diffuse into the tissues where it is needed. This is what Bohr effect tells us. According to Bohr effect, in environments where pH is low, carbon dioxide concentration is high, and temperature is high (all circumstances of metabolism) ... oxygen affinity for hemoglobin is low (resulting in a "right-shift");
Consider what happens in the lungs, where oxygen concentration is extremely high. Would you expect the affinity for oxygen in hemoglobin to be high or low? Because of the dense concentration of oxygen, the affinity for it is extremely high (a "left-shift"). In fact, binding of oxygen to one subunit of hemoglobin increases the affinity for more oxygen to bind to the other subunits (a cooperative effect); likewise, we can think of this environment just the opposite of metabolic tissues: low pH (because CO2 is being readily exhaled) and low temperatures. This is also why divers breath rapidly before diving. They want for increase the affinity for oxygen to hemoglobin and knowing what you now know about the conditions that effect hemoglobin affinity, you can fully appreciate what's happening.
If you try to remember random facts: ie. what happens when pH is low or high -- without fully understanding it conceptually, and being able to reason it out, I promise you'll forget it. But if you instead try to think of it like I just described, you'll remember it for good, I promise. Essentially the only 3 things really worth memorizing and they're all fairly straight forward is the equation above, and understanding whether left/right shift is refering to decreased/increased affinity for oxygen to hemoglobin (but even this can be deduced from a graph, if provided). The rest can be easily deduced with reason -- and God knows, we don't need to memorize any more stuff 😛
NOTE 1: Sometimes they do mention carbon monoxide and it's effect on Bohr effect, and the key thing about CO is that it binds very strongly to hemoglobin (ever hear of carbon monoxide poisoning; happens when people leave their car running with the garage door closed). The increased affinity for CO makes it difficult for hemoglobin to bind to O2, and because oxygen can't get to our tissues, ATP production halts and cellular metabolism essentially halts resulting in death.
NOTE 2: CO contains oxygen, and because CO affinity for hemoglobin is so high, it results in a left-shift (Bohr effect) -- because it's bound so tightly and there is no dissociation. This might seem counter intuitive, but remember Bohr effect simply describes the affinity of hemoglobin to oxygen -- not necessarily O2.
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Also, in regards to the buffering capacity of bicarbonate. The pKa of Carbonic Acid (H2CO3) is near physiological pH. However, we generally tend to think of CO2 as our acid and HCO3- as our conjugate base (in HH equation -- our buffering system). Both of these are in really high concentrations within our body, in roughly a 50:50 amount, which makes them an excellent buffer that helps us resist changes in pH. However, depending on certain conditions (low or high CO2/HCO3-), our pH can increase or decrease. But the change is typically very insignificant, again, because it's a great buffering system.
I could really go on and on about buffering systems and how they relate to HH, conceptually, but I feel like I've said too much already and you probably have a decent understanding of it anyways 🙂
Hope this helps a bit.
