Lab: Equillibrium
Name:_____________________________
Background: Hemoglobin is a protein found in red blood cells that binds to oxygen in the lungs and
transports it throughout the body. We can use the concept of chemical equilibrium to understand this
process. The chemical symbol for the complex hemoglobin molecular structure will be Hgb. The
chemical reaction for the binding of oxygen is:
Hgb(aq) + 4O2(g)
Hgb(O2)4(aq)
According to the chemical reaction, each hemoglobin molecule is capable of binding how many oxygen
molecules? _____________
The double arrows (
) indicate that this chemical reaction is reversible.
What do you think this means? _______________________________________________________
_________________________________________________________________________________
A number of factors can influence the direction in which a reversible reaction can proceed. One of
those factors is the concentration of reactants and products. When the concentration of reactants is
increased, the reaction will proceed mostly toward the right. When the concentration of products is
increased, the reaction will proceed mostly to the left. Color code the diagram below. Use red for
oxygenated blood and blue for deoxygenated blood.
In the lungs, there is a high concentration of O2
from the air. The blood has been depleted of
oxygen so the concentration of HgB(O2)4 is
_________. Therefore, the favored direction of
the reaction in the lungs would be:
Hgb + 4O2 __________ Hgb(O2)4
The blood, in the capillaries of the body, has a
high concentration of Hgb(O2)4. The tissues of
the body have used up their oxygen and have a
____________ concentration of O2. Therefore,
the favored direction of the reaction in the
capillaries of the body would be:
Hgb + 4O2 _______ Hgb(O2)4
Analysis part I
Explain how the effect of reactant and product concentrations on the direction of reactions allows
hemoglobin to transport oxygen from the air to the cells of the body, using very little energy.
Part Ii: Background: When people travel to the mountains, they often feel tired and light-headed for
some time. That’s because the mountain air contains fewer oxygen molecules. This causes a shift in the
hemoglobin – oxygen reactions.
In the mountains:
Hgb + 4O2
Hgb(O2)4
Analysis (part II)
1. Why is the reverse arrow longer than the forward arrow?
2. How did the change in [O2] affect the chemical equilibrium of the reaction?
3. Describe what happens to the O2 that is attached to the hemoglobin in the blood.
4. Write the reaction that describes your response to #3.
5. It is impossible to add more O2 to the air. Describe one way that the body can compensate for
the decrease in [O2] and restore the chemical equilibrium.