1. 1. Hemoglobin and the Movement of Oxygen
M 221 Medical Biochemistry
Fall 2017
Dr. Nabil Bashir

2. Hemoglobin and the Movement of Oxygen Specific objectives
The student must understand the process of oxygen binding, specifically;
Oxygen binding and iron movement - deoxy versus oxygenated state 
Iron-oxygen binding 
Quaternary structure of deoxyhemoglobin 
Oxygen binding of myoglobin 
Oxygen binding of hemoglobin 

3. Hemoglobin and the Movement of Oxygen Specific objectives
2. The student must understand the concept of cooperativity, specifically;
Cooperativity in hemoglobin's oxygen binding 
Quaternary changes on oxygen binding by hemoglobin 
T to R transition 
Sequential model of binding 
The effect of 2,3 BPG 
Binding of 2,3BPG to hemoglobin 
Oxygen binding and fetal hemoglobin 

4. Hemoglobin and the Movement of Oxygen Specific objectives
3. The student must understand molecular aspects of Bohr Effect, specifically;
Effect of pH on oxygen affinity of hemoglobin 
Carbon dioxide and pH 
Carbon dioxide effects 
Carbamate formation 
Transport of CO2 to lungs 

5. Hemoglobin and the Movement of Oxygen Specific objectives
4. The student must know some Hemoblobin Genetic Considerations;
Sickled blood cells  and hemoglobin fibers 
Sickle cell traits and malaria 

6. Hemoglobin and the Movement of Oxygen
Introduction
Animals Have Widely Varying Needs for Oxygen
Demand for Oxygen Can Change in Seconds
Basal Needs are Significant - Diffusion not Enough
Exercise, Fight/Flight Add to the Need
ATP Energy Produced Aerobically 15 Times More Efficiently Than Anaerobically
Respiration versus Fermentation
Efficient, Adaptable Oxygen Delivery is Necessary

7. Quaternary Structure
Interaction of multiple protein subunits
Hemoglobin - 4 Subunits (α2β2), 1 Heme Each, 1 O2 Each, 1 “Donut Hole”
Myoglobin - 1 Subunit, 1 Heme, 1 O2 Each

8. Hemoglobin and the Movement of Oxygen
Structure and Function
Heme Prosthetic Group
Ferrous Iron - Methemoglobin Won’t Work
Only Fe++ Binds Oxygen

9. Hemoglobin and the Movement of Oxygen
Structure and Function
Edge-on View
Attached to Remainder of
Global Subunit
Histidine’s Movement
Changes
Global Unit’s Shape

10. Hemoglobin and the Movement of Oxygen
Cooperativity
Affected by
O2 Binding
)R-State)0
Fully Oxygenated
(R-State(
No Oxygen
)T-State(
Exiting
Lungs
Entering
Lungs
Oxygen Bound
Affected by
O2 Binding
R-State
Binding of the first O2 favors binding of second, etc. - Cooperatively
Cooperatively Important as Hemoglobin Rapidly Passes Through Lungs

11. Hemoglobin and the Movement of Oxygen
At High O2, Both Hold 100%
Hemoglobin and the Movement of Oxygen
Cooperativity
At Low O2, Myoglobin Holds
More than Hemoglobin
Hyperbolic Binding Curve
Sigmoidal Binding Curve
As Curves Move to Right
Less Affinity for Oxygen
Myoglobin Better for Storing Oxygen
Hemoglobin Better at Delivering Oxygen

12. Hemoglobin and the Movement of Oxygen
Bohr Effect
Less Oxygen Bound at Same Pressure
Less Affinity
More Affinity
Protons Can Bind to Hemoglobin
Protons Change Hemoglobin’s Shape
Reshaped Hemoglobin Loses Oxygen
Rapidly Metabolizing Tissues Release Protons
Rapidly Metabolizing Tissues Get More Oxygen From Hemoglobin
More O2 Required To Have
Same Fraction Bound

13. Hemoglobin and the Movement of Oxygen
Bohr Effect & CO2
Acid Favors Release of O2 From Hemoglobin
CO2 Favors Release of O2 From Hemoglobin
Acid and CO2 are Released by Rapidly Metabolizing Tissues

14. Hemoglobin and the Movement of Oxygen
2,3 BPG
Byproduct of Glycolysis
Exercising Muscle Cells Rapid Use Glycolysis
Exercising Muscle Cells Produce Acid, CO2, and 2,3 BPG
Binds in Hole of Donut
Locks Hemoglobin in T-State
2,3 Bisphosphoglycerate

15. Hemoglobin and the Movement of Oxygen
2,3 BPG and Oxygen Binding
Slow Metabolic Rate
Rapidly Metabolizing Cells Produce Acid
Rapidly Metabolizing Cells Release CO2
Rapidly Metabolizing Cells Release 2,3 BPG
All Favor O2 Release from Hemoglobin So
Rapidly Metabolizing Cells Get More O2
Fast Metabolic Rate

16. Hemoglobin and the Movement of Oxygen
2,3 BPG and Smoking
2,3 BPG Big Concern for Smokers
Blood of Smokers has High Levels of 2,3 BPG
Hemoglobin Gets Locked in T-state in Passage Through Lungs
Oxygen Carrying Capacity of Blood Reduced
Carbon Monoxide Levels Also Higher in Smokers
2,3 Bisphosphoglycerate

17. Hemoglobin and the Movement of Oxygen
Movement of CO2
HbO + H+ O2
Blood
Rapidly
Metabolizing Tissue
H+:Hb-CO2
Some
Remainder
H2O
Blood
H+:Hb-CO2
HbO
Exhaled
HbO
H2O + CO2
Lungs
O2 + H+:Hb-CO2

18. Hemoglobin and the Movement of Oxygen
Carbon Monoxide and Heme
An Additional Histidine is Present at the Heme Iron Site
Reduces Affinity to CO, but Does Not Eliminate it
Carbon Monoxide in Cigarette Smoke
Note That CO2 Does Not Bind to Heme, nor do Protons

19. Hemoglobin and the Movement of Oxygen
Fetal Hemoglobin
The Body Makes Different Globins Over Time
Most Variations Centered on Birth
Fetal Hemoglobin Mostly α2γ2
High Most of Life
At Adult Levels by 24 Weeks
Highest in Fetus

20. Hemoglobin and the Movement of Oxygen
Fetal Hemoglobin
Fetal Hemoglobin Can’t Bind to 2,3 BPG
Mostly Remains in R-state
Increasing Affinity

21. Hemoglobin and the Movement of Oxygen
Sickle Cell Anemia
Sickle Cell Anemia is a Genetic Disease Affecting Hemoglobin
Multiple Forms - Mutation of Glu to Val at Position #6 Most Common
Red Blood Cells Lose Rounded Shape and Form Sickles
Shape Change Happens in Low O2 Conditions - Exercise
Change Caused by Polymerization of Hemoglobin
Sickled Cells

22. Hemoglobin and the Movement of Oxygen
Sickle Cell Anemia
Rounded Cells Move Easily Through
Capillaries
Sickled Cells Get Stuck
Sickled Cells Removed by Spleen

23. Hemoglobin and the Movement of Oxygen
Sickle Cell Anemia
Why is Sickle Cell Anemia so Widespread?
Why Has it Not Been Selected Against?
Greatest Incidence of Sickle Cell Anemia
Greatest Incidence of Malaria

24. Hemoglobin and the Movement of Oxygen
Sickle Cell Anemia
Benefit of Sickle Cell Mutation for Heterozygotes
No Benefit to Homozygous Recessive or Dominant

25. Hemoglobin and the Movement of Oxygen
Summary
Animals Have Widely Varying O2 Needs
ATP Generated Much More Efficiently in Presence of O2
Hemoglobin and Myoglobin are Related, but Have Different Functions
Hemoglobin has Four Subunits and Hemes. Myoglobin has One of Each
Bind of O2 by Heme’s Iron Pulls up on a Histidine and Change’s Hemoglobin’s Shape
Changing Hemoglobin’s Shape Converts Hemoglobin from T-state to R-state
R-state Binds Oxygen Better. T-state Releases O2 Better
In the Bohr Effect, Binding of CO2 and H+ Favors O2 Release
The Bohr Effect Explains How Oxygen and CO2 Exchanged in Lungs
2,3 BPG is Produced by Rapidly Metabolizing Cells. It too Favors O2 Release
Fetal Hemoglobin Can’t Bind 2,3 BPG and has Greater O2 Affinity Than Adult Hemoglobin
Sickle Cell Anemia (SCA) is a Genetic Disease of Hemoglobin
In Low O2 Concentration, Red Blood Cells of SCA Sufferers Form Sickle Shapes
Sickled Cells Stick in Capillaries and Can be Fatal
People Heterozygous for the Mutated Gene Survive Malaria Better Than Others