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39 Cards in this Set

  • Front
  • Back
What chromosomes encode Hb a and Hb B?
Hb A = Ch' 16
Hb B = Ch' 11
What is the makeup of:
A = a2b2 - alpha/beta
A2 = a2d2 - alpha/delta
F = a2y2 - alpha/gamma
What ch' carries the delta and gamma genes?
Ch' 11 - along with Beta
What causes B-thalassemia?
Mutations that affect chain termination, transcription activation, and RNA processing.
What is thalassemia?
Imbalance in concentration of alpha/beta chains.
What causes sickle cell disease?
-Point mutation of 6th pos on B-chain; Val replaces Glu
What inheritence pattern is exhibited by SS disease?
Homozygous recessive
What DNA technology is used to identify SC mutation?
Is HPFH always caused by genetic deletions/mutations?
No; it is also seen in thalassemias.
How are myoglobin and hb different?
Hb exists as a heterodimer, four subunits; Myoglb exists as a monomeric protein.
What is the function of Myoglb and Hb?
Hb - transports oxygen

Myoglb - stores oxygen
What is the same in Hb and Myoglb?
Both have protoporphyrin IX prosthetic group containing Iron.
What form must Iron be in to bind O2?
Ferrous; if it is oxidized to Ferric FE3+ it can't bind.
What is Hb called when oxidized?
Which has a higher P50; myoglb or Hb?
Hb - it releases its O2 much sooner than Myogbn, which prefers to wait to release O2 to working muscle where the PO2 is much lower than in veins.
How does Hb's conformation change as it picks up O2 molecules?
Taut -> relaxed.
How does conformation shifting affect Hb's O2 affinity?
It increases.
What molecule facilitates o2 release by Hb?
How is the iron within Heme's protoporphyrin ring shifted when it binds O2?
O2 binding Iron shifts the Histidine that Fe is bound to; this AXIAL LIGAND transmits the binding to the subunit.
What is the K effect?
The effect of an allosteric regulator binding a protein to induce a conform. change that alters its affinity for substrate.
What is the V effect?
The effect of an allosteric regulator binding a protein to induce a conform. change that alters its Vmax.
What are allosteric regulators of Hb?
DPG and CO2 and H+
What kind of effectors are DPG , CO2, and H+?
Negative allosteric effectors.
What is the Bohr effect?
The reciprocal relationship between the effectors O2 and H+
How does O2 effect Hb?
It causes Hb to release H+ and CO2 and instead bind O2.
What's another name for th Bohr effect?
Isohydric shift
What 2 amino acid residues are responsible for the Bohr affect?
Asp 94
His 146
How does Asp 94 alter Hb?
How does His 146?
In deoxyHb, Asp 94 is in close proximity to His 146; the neg charge on Asp favors protonation of His.
What type of effect is this interaction between Asp/His called?
Charge microenvironment effects.
How does protonation in the tissues cause deoxygenation of Hb?
The protonation of His is transfered via conformation shift to the heme ring and promotes deoxygenation. Because CO2 has high affinity, it binds Fe.
Where is the binding site of 2-3,DPG on hemoglobin?
In a central cavity between the Beta subunits.
How dose 2-3,DPG bind Hb?
By ionic bonds.
How exactly does the genetic substitution in HbS lead to symptoms?
Polymerization of Hb occurs when it is deoxygenated; Intracellular fibers cause sickling, clogs microvessels.
What happens to the globin chains in sickle cell disease?
They become sticky and polymerase due to interaction of amino acid residues.
What 3 variables affect the degree of polymerization in HbS?
1. Degree of deoxygenation
2. Intracel. Hb concentration
3. Amt of HbF present.
How does HbF affect HbS?
Inhibits polymerization because of a Glu residue at pos. 87 of y chain; prevents a lateral contact in the sickle cell fiber.
What 2 other abnormalities in RBCs result from the membrane deformation caused by sickling?
1. Dysreglulation of cell vol due to Ca2+ leakage (into cell)
2. Adhesion to microvessels due to incr. surface proteins exposed.
What is the therapeutic affect of hydroxyurea?
-Stimulation of HbF production
What 2 methods are used to monitor Hb constitution?