| Term | Definition |
|---|
| Globin fold | 3d structure consists solely of 8 a-helices |
| large ring network with iron at center | describe structure of globin prosthetic group |
| myoglobin | monomer with single heme bound, single O2 site, and histidyl group ligated to iron |
| hemoglobin | tetramer with 4 O2 sites, binds 2,3BPG and protons |
| Y = [O2]/(Kd + [O2]) | Fractional saturation equation for myoglobin |
| Y = [L]^n/(K^n + [L]^n), n=binding coeff | Hill equation |
| [P]+[PL] | what is the value of Pt? |
| Y=[PL]/[Pt] | how does Y relate to Pt? |
| [PL]=[Pt][L]/(Kd+[L]) | what is the equation for a binding isotherm? |
| n=1 no cooperativity, n>1 positive coop, n<1 negative coop | explain how values of n describe binding cooperativity |
| Mb is hyperbolic (one binding site) and Hb is sigmoidal (4 binding sites, 4 possible cooperative equilibriua -- homotropic effect) | What are the shapes of Mb and Hb binding isotherm plots? |
| [PL]=[Pt][L]/(Kd + [L]) | Fractional saturation equation 2 |
| Relaxed=high affinity, Taut=low, and conformers are symmetric (T4 or R4) | Monod model for positive cooperativity |
| Koshland model | symmetry not required, can explain positive or negative cooperativity, ligand binding induces T->R, subunits influenced to transition (T/R) by its neighbors |
| for greater n>1, more sigmoidal binding isotherm, for n<<1, more hyperbolic | describe effect of Hill coeffcient on shape of binding isotherm |
| low oxygen favors T state | what state is favored in the Monod model with low oxygen? |
| O2 affinity increases with Y | how is O2 affinity affected by fractional |
| Kd | dissociation constant |
| Fe moves into p lane of heme, C-terminus displaced, diminshed subunit interactions, thus cooperative O2 binding | describe Hb structural changes upon binding O2 |
| Fe2+ -> Fe3+ | how does binding of oxygen change iron's oxidation state? |
| taut state, so lower O2 affinity | what happens to Hb when His146 is protonated and a salt bridge forms across His146/Asp94? |
| N-terminus of Deoxyhemoglobin a-subunit, forms salt bridge between Val-Arg | where does CO2 bind to Hb? |
| Bicarbonate, HbCO2, CO2 | rank in order of highest to lowest the most common forms of CO2 in the body |
| carbonic anhydrase | second most common protein in RBCs, this aids in forming bicarbonate from water and CO2 |
| Bohr effect | decrease in Hb affinity for oxygen by binding of CO2 and acid |
| decreases O2 affinity | a decrease in pH has this effect on Hb |
| O2 and CO2 have reciprocal effects and are heterotropic effectors, so ligration of O2 promotes CO2 release | explain the Haldane effect |
| Binds one molecule of BPG between (+) B-subunits and reduces affinity for O2 (fetal Hb has low BPG affinity due to alpha/gamma structure instead of alpha/beta) | explain effect of 2,3BPG binding Hb |
| Decrease O2 affinity, CO2 having greater effect | What are the effects of H+, 2,3BPG, and CO2 on Hb O2 affinity? |
| Binds to deoxy form to decrease O2 affinity and forms salt bridge between a-Arg and a-N-terminus | what is effect of Cl- on Hb? |
| Co affinity is 200 times greater than O2 affinity, and it binds in same place | discuss CO binding in Hb |
| O2 can still be released in peripheral tissues with 50% Hb, but cannot wth 50% CO-bound Hb. It also binds to cytochrome C oxidase and myoglobin, which increase toxcity | why is CO so toxic? |
| Ferric state (non-functional) | what is name of state of Fe3+ |
| Maternal Hb->Fetal Hb->Fetal Mb->Cytochromes | flow of O2 from mom to baby |
| Glu->Val | This mutation causes sickle cell disease |
| Glu->Lys, RBCs->target cells with intercellular crystals | this mutation causes Hb C disease, more severe than Hb S |
| Dense, malformed, and angular cells with target cells present | cell morphology in Hb SC disease |
| Hb poymerizes inside the cell in deoxy form which creates long fibers that cause sickling | What is basis of morphology of sickle cells? |
| Even after Hb is oxygenated, shape change is permanent duje to changes in cytoskeleton of RBC | describe irreversible sickling |
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