| Explain the relationships between Kd, ligand concentration and fraction of receptors occupied with ligand? | Kd = concentration of ligand at which 50% of receptors (R) are occupied , The fraction of bound sites depends on the free ligand concentration and Kd. |
| why is there a wide range of affinities in ligand receptor interactions? | -Because Conformational changes may occur upon ligand binding called an induced fit and it allows for tighter binding of the ligand high affinity for different ligands. These changes can happen to the ligand and the protein. |
| What is induced fit? | Conformational changes may occur upon ligand binding
– This adaptation is called the induced fit
– Induced fit allows for tighter binding of the ligand
– Induced fit allows for high affinity for different ligands
• Both the ligand and the protein can change their conformations |
| Why myoglobin is not used for oxygen transport? | Myoglobin is the main oxygen storage protein
Because it has a very strong affinity for oxygen
Also it’s structure prevents super oxide (O2-) from leaving the heme group |
| Explain 4 mechanisms of an allosteric regulation of Hb binding to O2 that facilitate O2 transport? | 2,3-Bisphosphoglycerate Another heterotropic allosteric regulator of O2 Binding to Hemoglobin
• 1- Negative heterotropic regulator of O2 binding.
• 2- Present at mM concentrations in erythrocytes
– Produced from an intermediate in glycolysis
• 3- Small negatively charged molecule, binds to the positively charged central cavity of Hb
• 4- Stabilizes the T states
The Ph difference between lungs and tissue increases efficiency of the O2 transport(Bohr effect). undergoing a transition from a low-affinity state (the T state) to a high- affinity state (the R state) as more O2 molecules are bound. |
| What is the T state of hemoglobin? | • T = Tense state,
– More interactions, more stable – Lower affinity for O2 |
| What is the R state of hemoglobin? | R = Relaxed state,
– Fewer Interactions, more flexible – Higher affinity for O2 |
| What is homotropic allosteric regulation? | In a multisubunit protein, the binding of a ligand to one subunit may change receptor conformation and ligand binding to other subunits. This is homotropic allosteric cooperativity |
| What is heterotropic allosteric regulation? | Receptor-Ligand binding can be regulated by other molecules. This is heterotropic allosteric cooperativity |
| Give 4 examples of allosteric regulation of oxygen binding to hemoglobin? | 2,3-Bisphosphoglycerate
pH —> concentration of H+ and CO2
Transition from T to R state |
