Hemoglobin (Hb) is a blood protein that is responsible for...

Hemoglobin (Hb) is a blood protein that is responsible for transporting oxygen. It can exist in the protonated form as $\mathrm{HbH}^{+}$. The binding of oxygen can be represented by the simplified equation $$\mathrm{HbH}^{+}+\mathrm{O}_{2} \rightleftharpoons \mathrm{HbO}_{2}+\mathrm{H}^{+}$$ (a) What form of hemoglobin is favored in the lungs where oxygen concentration is highest? (b) In body tissues, where the cells release carbon dioxide produced by metabolism, the blood is more acidic due to the formation of carbonic acid. What form of hemoglobin is favored under this condition? (c) When a person hyperventilates, the concentration of $\mathrm{CO}_{2}$ in his or her blood decreases. How does this action affect the above equilibrium? Frequently a person who is hyperventilating is advised to breathe into a paper bag. Why does this action help the individual?

Key Concepts

Hemoglobin Oxygen Binding

This concept describes the ability of hemoglobin, a protein found in red blood cells, to bind oxygen in the lungs and transport it to tissues. The binding involves a reversible interaction, where hemoglobin can pick up oxygen in high oxygen concentration environments and release it in areas where oxygen is low, thus fulfilling a critical role in the body’s respiratory and circulatory systems.

Bohr Effect

The Bohr Effect explains how changes in blood pH and carbon dioxide concentration affect the oxygen affinity of hemoglobin. In environments where the blood becomes more acidic (such as in metabolically active tissues releasing carbon dioxide), hemoglobin releases oxygen more easily. Conversely, in the lungs where oxygen concentration is high and pH is higher, hemoglobin holds on to oxygen, facilitating efficient oxygen uptake.

Le Chatelier's Principle in Biochemical Equilibria

Le Chatelier's Principle is a general rule that predicts how a change in conditions (such as concentration, pressure, or temperature) will shift a chemical equilibrium in order to re-establish balance. In the context of hemoglobin's oxygen binding, this principle helps explain how shifts in the concentrations of oxygen, carbon dioxide, and hydrogen ions will favor either the oxygenated or deoxygenated form of hemoglobin.

pH and Carbonic Acid Generation

The pH of blood is closely linked to the concentration of hydrogen ions, and the formation of carbonic acid from carbon dioxide and water plays a significant role in regulating this pH. In tissues where metabolic activity produces carbon dioxide, the conversion to carbonic acid leads to a lower pH, causing hemoglobin to release oxygen more readily as part of the oxygen delivery process.

Hyperventilation Effects

Hyperventilation reduces the carbon dioxide levels in the blood, which in turn decreases carbonic acid formation and raises the pH. This shift affects the equilibrium of oxygen binding by promoting the formation of the oxygenated form of hemoglobin. Breathing into a paper bag helps to re-increase carbon dioxide levels, thus restoring the acid-base balance and mitigating the excessive alkalinity caused by hyperventilation.

Transcript

00:01 We're going to be discussing hemoglobin and equilibrium.

00:04 For this question, we have three situations, and in each of those situations, situations will decide which side of this equation of this chemical reaction is favored and what product we are trying to get because of that situation.

00:21 Okay, for our first question, let's go with this color.

00:26 For our first scenario, which form of hemoglobin, that'll be, either this or this, one of those two, is favored in the lungs, in the lungs which have high o2 concentration.

00:46 So if i have high o2 concentration, as i do in the lungs, which side of this equation would be favored? well, if we increase the concentration of o2, we will shift right, and the hb o2 would be favored.

01:01 The hb .o .2 would be favored.

01:03 The hb .o .2 would would be favored in the lungs.

01:09 Okay.

01:12 And let me try to erase a couple of these.

01:18 Sorry if it's not perfect, but i'm sure you'll figure it out.

01:21 Okay.

01:23 Now for our second scenario, let's read what our second scenario is.

01:31 B, embodied tissues.

01:33 Cells are releasing co2.

01:37 So co2 is released during metabolism to tissues in the body.

01:45 So you have a little excess co2.

01:48 And then that's going to form.