Chapter 14 Chemical Equilibrium 2011, NKMB Co., Ltd. Chemistry, Julia Burdge, 2 st Ed. McGraw Hill. Mr. Truong Minh Chien ; losedtales@yahoo.com http://tailieu.vn/losedtales http://mba-programming.blogspot.com 2 Hemoglobin • protein (Hb) found in red blood cells that reacts with O 2  enhances the amount of O 2 that can be carried through the blood stream Hb + O 2 ⇔ HbO 2  the Hb represents the entire protein – it is not a chemical formula  the ⇔ represents that the reaction is in dynamic equilibrium Chemistry, Julia Burdge, 2 nd e., McGraw Hill. 3 Hemoglobin Equilibrium System Hb + O 2 ⇔ HbO 2 • the concentrations of Hb, O 2 , and HbO 2 are all interdependent • the relative amounts of Hb, O 2 , and HbO 2 at equilibrium are related to a constant called the equilibrium constant, K  the larger the value of K, the more product is found at equilibrium • changing the concentration of any one of these necessitates changing the other concentrations to reestablish equilibrium Chemistry, Julia Burdge, 2 nd e., McGraw Hill. 4 O 2 Transport Hb + O 2 ⇔ in the lungs, with high concentration of O 2 , the equilibrium shifts to combine the Hb and O 2 together to make more HbO 2 in the cells, with low concentration of O 2 , the equilibrium shifts to break down the HbO 2 and increase the amount of free O 2 HbO 2 O 2 in lungs Hb HbO 2 O 2 in cells Chemistry, Julia Burdge, 2 nd e., McGraw Hill. 5 HbF Hb Fetal Hemoglobin, HbF HbF + O 2 ⇔ HbFO 2 • fetal hemoglobin’s equilibrium constant is larger than adult hemoglobin • because fetal hemoglobin is more efficient at binding O 2 , O 2 is transferred to the fetal hemoglobin from the mother’s hemoglobin in the placenta Hb + O 2 ⇔ HbO 2 O 2 HbO 2 O 2 Hb + O 2 ⇔ HbFO 2 HbFO 2 O 2 Chemistry, Julia Burdge, 2 nd e., McGraw Hill. 6 Oxygen Exchange between Mother and Fetus Chemistry, Julia Burdge, 2 nd e., McGraw Hill. 7 Reaction Dynamics • when a reaction starts, the reactants are consumed and products are made  forward reaction = reactants → products  therefore the reactant concentrations decrease and the product concentrations increase  as reactant concentration decreases, the forward reaction rate decreases • eventually, the products can react to reform some of the reactants  reverse reaction = products → reactants  assuming the products are not allowed to escape  as product concentration increases, the reverse reaction rate increases • processes that proceed in both the forward and reverse direction are said to be reversible  reactants ⇔ products Chemistry, Julia Burdge, 2 nd e., McGraw Hill. 8 Hypothetical Reaction 2 Red ⇔ Blue Time [Red] [Blue] 0 0.400 0.000 10 0.208 0.096 20 0.190 0.105 30 0.180 0.110 40 0.174 0.113 50 0.170 0.115 60 0.168 0.116 70 0.167 0.117 80 0.166 0.117 90 0.165 0.118 100 0.165 0.118 110 0.164 0.118 120 0.164 0.118 130 0.164 0.118 140 0.164 0.118 150 0.164 0.118 The reaction slows over time, But the Red molecules never run out! At some time between 100 and 110 sec, the concentrations of both the Red and the Blue molecules no longer change – equilibrium has been established. Notice that equilibrium does not mean that the concentrations are equal! Once equilibrium is established, the rate of Red molecules turning into Blue is the same as the rate of Blue molecules turning into Red . Chapter 14 Chemical Equilibrium 2011, NKMB Co., Ltd. Chemistry, Julia Burdge, 2 st Ed not a chemical formula  the ⇔ represents that the reaction is in dynamic equilibrium Chemistry, Julia Burdge, 2 nd e., McGraw Hill. 3 Hemoglobin Equilibrium