Chapter 5 Flashcards
Describe cooperative binding
“Snow ball effect” where binding of one oxygen breaks and reforms bonds, which leads to other heme subunits having a higher affinity for oxygen
Pharmacophore
A part of a molecular structure that is responsible for a particular biological or pharmacological interaction that it undergoes
Hemoglobin characteristics (6)
- 4 heme strucutures
- 4 binding sites
- Lower affinity for O2
- Sigmoidal
- Cooperativity
- O2 transport
Myoglobin characteristics (6)
- 1 heme structure
- High affinity for O2
- No cooperative binding
- O2 bound at any concentration
- Hyperbolic growth
- O2 storage
Myoglobin and Hemoglobin similarities
- Ring polythirin
- Chelate Fe2+ in middle of structure
- Proximal and distal histidine
- Globular proteins
- Both bind O2
What are the benefits of using protein-heme-iron system vs. free iron for oxygen transport
Free floating Fe2+ would most likely oxidize Fe2+ to ferric Fe3+, which would lose the function to bind to oxygen. Hemoglobin protects Fe2+ and is able to convert Fe3+ back to Fe2+ after it is bound to oxygen
Proximal histidine characteristics
- Anchors Fe3+ in heme structure
- Close to heme ring
Distal histidine characteristics
- Closer to O2
- Helps protect O2 binding site
- Helps keep CO from binding
- Makes O2 bind at angle
T State characteristics (5)
-Low O2 (not bound)
-Starts at tissues, goes to lungs, turns into R state
-Large pocket
-Stable
Inactive/deoxygenated
R State characteristics (5)
- High O2
- Starts at lung, goes to tissues, turns into T state
- O2 bound
- Increase O2 affinity
- Small
Explain coopertivity in relation hemoglobin
When the first O2 binds to Hb, it interacts with the entire ring by stretching it. This increases the affinity that 2,3,4 subunits have for O2, making it easier for them to be bound to O2. Opposite is true for releasing O2.
Coordinate covalent bonds
Four pyro nitrogens donate electrons to Fe2+ group in the middle of hemoglobin
Why does hemoglobin have a higher affinity for CO than O2
Hemoglobin has a higher affinity for CO because it is smaller and it forms bonds at a straight angle. Triple bound C to O has a smaller distance than double bound O to O
Sickle cell anemia is caused by what mutation?
Glu –> Val at 6th position, in beta globin chain of hemoglobin, which changes from a polar to nonpolar amino acid
What are the ramifications of sickle cell anemia mutation
Mutation causes RBC to change its shape, which decreases O2 carrying capacity and elasticity.
