Term
| What is the globin molecule discussed in class that contains only 1 heme group? |
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Definition
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Term
| How many residues is Myoglobin? What predominantely composes it's secondary structure? |
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Definition
| 153 residues, most in 8 alpha helices |
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Term
| Chemically, what does a heme group look like? |
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Definition
| A heme group is 4 pyrrole groups (nitrogen containing rings) linked by methene bridges with a Fe2+ in the center |
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Term
| How many heme groups does Hemoglobin contain? |
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Definition
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Term
| In myoglobin, what two residues help hold the Heme group in place? What type of interaction is stabilizing the Heme group? |
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Definition
| Valine and Phenylalanine. Hydrophobic Interactions |
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Term
| How does the heme group allow for reversible binding of O2 to Fe2+? |
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Definition
| The heme group prevents the Iron(II) from being oxidized |
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Term
| What is metmyoglobin (or methemoglobin)? |
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Definition
| This is a myoglobin in which the Iron has been oxidized to 3+ |
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Term
| What is the role of myoglobin? |
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Definition
| Myoglobin allows for better perfusion of oxygen into muscle tissues by binding the O2. Unbound O2 has low solubility and therefore does not diffuse well across tissues |
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Term
| What is the dissociation constant? |
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Definition
A measure of how much a compound dissociates into smaller components.
Mathematically
[molecule][ligand]/[molecule-ligand compound]
[] denotes concentration |
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Term
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Definition
| p50 is defined as the pressure at which half of the compound is oxygenated and the other half dissociated |
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Term
| What is the shape of the hemoglobin protein? |
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Definition
| tetrameric protein composed of 2 sets of alpha beta protomers |
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Term
| What type of interactions do the alpha and beta structures within hemoglobin exhibit? |
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Definition
| Primarily hydrophobic. Interactions occur extensively across unlike subunites (i.e. between alpha and beta units) |
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Term
| Why does most hemoglobin interaction occur between alphas and betas and not between like chains? |
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Definition
| Alpha-Alpha and Beta-Beta interactions are limited due to a solvent filled channel that separates them |
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Term
| Binding of O2 to hemoglobin causes what kind of structural change? |
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Definition
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Term
| What is the shape of the hemoglobin O2 dissociation curve? |
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Definition
| Sigmoidally shaped. This type of curve is suggestive of cooperative binding |
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Term
| What is the shape of the myoglobin O2 dissociation curve? |
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Definition
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Term
| Hemoglobin exhibits what kind of binding system? |
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Definition
| positively cooperative binding system. Meaning that for each oxygen that binds to a hemoglobin, the O2 affinity rises |
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Term
| What does it mean is the slope of a hill curve (the hill coefficient) is 1? |
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Definition
| If n=1 then the system is noncooperative |
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Term
| What does it mean is the slop of a hill curve (hill coefficient) is greater then 1? |
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Definition
| if the slope is greater then 1 then the binding system is positively cooperative |
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Term
| What does it mean if the slope of a hill curve (hill coeffecient) is less than 1? |
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Definition
| The system is negatively cooperative |
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Term
| What is an allosteric effect? |
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Definition
| When the binding of 1 ligand affects the affinities of remaining unfilled binding sites. Can be homotropic or heterotropic |
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Term
| What is the effect of the T state on O2 binding in hemoglobin? |
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Definition
| The T state means that binding affinity for O2 is low |
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Term
| What is the effect of the R state of Hemoglobin on 02 binding affinity? |
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Definition
| The R state has high affinity of O2 |
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Term
| How do the changes in tertiary and Quaternary structure change when Oxygen binds to Hemoglobin? |
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Definition
| When Oxygen binds to the Fe(II) it pulls the molecule which then pulls on Histidine 8, shifting the structure |
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Term
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Definition
| As serum pH decreases so too does the hemoglobin O2 binding affinity. Causes a right shift in the curve |
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Term
| What is the haldane effect? |
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Definition
| Describes the properties of Hemoglobin in regards to transport of CO2. Deoxygenated blood has a higher affinity for CO2 then oxygenated blood. Results in CO2 being collected in the tissues and released in the lungs |
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Term
| What is the isohydric shift? |
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Definition
| describes the transformations that CO2 takes, predominantely being transported as Bicarb |
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Term
| Why is the isohydric shift favorable for C02 uptake and O2 perfusion? |
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Definition
CO2 undergoes a series of reversible transformations:
C02 + H2O->H2CO3
H2CO3(carbonic acid) -> H+ + HCO3- (bicarb)
Since DeoxyHb is a weaker acid than OxyHB it readily picks up Bicarb (Haldane effect). Protonation of the HB amino acids furthermore lowers Hemoglobin O2 affinity (Bohr effect) |
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Term
| Besides transport as bicarb, how else can C02 be taken away from tissue and to the lungs? |
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Definition
1) Covalent and reversible binding to Hemoglobin
2) in blood serum as dissolved compound |
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Term
| How does 2,3-Bisphosphoglycerate(BPG) affect the Hemoglobin O2 dissociation curve? By what mechanism? |
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Definition
| BPG causes a right shift in O2 affinity by covalently attaching to Hemoglobin and stabilizing the T form of Hemoglobin (low affinity) |
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Term
| What does Fetal Hemoglobin have a higher O2 affinity then adult Hemoglobin? |
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Definition
| BPG does not bind as successfully to fetal hemoglobin as it does to adult hemoglobin |
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Term
| Why does BPG bind poorly to Fetal Hemoglobin? |
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Definition
| Fetal globin has 2 gamma sub-units (instead of beta, serine instead of histidine) which lowers BPG affinity |
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Term
| How does sickle cell anemia arise? |
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Definition
| it is a beta hemoglobin mutation that changes a Glutamate for a Valine |
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Term
| How do you screen for hemoglobinopathies? |
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Definition
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