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24 Cards in this Set
- Front
- Back
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At low oxygen tension, will there be higher oxygen affinity in hemoglobin or myoglobin
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Myoglobin
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comprises 574 amino acids in 4 polypeptide chains (globin
sub-units), held together by non-covalent interactions. Each globin contains a haem group(porphyrin ring) containing a ferrous ion that can reversibly bind an oxygen molecule. The subunits are identical in pairs (i.e. 2 of one kind and 2 of another). |
Hemoglobin
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Has evolved from the same ancestral polypeptide as hemoglobin.
It comprises a single polypeptide chain of 153 amino acids which very much resembles a single hemoglobin subunit and consequently can bind only one oxygen molecule. |
MYOGLOBIN
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75% of hemoglobin structure is _
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Alpha helix
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Heme group is _
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Porphyrin ring (protoporphyrin IX)
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What gives color to the blood?
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Absorption of light by heme
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Can bind to hemoglobin with 2000 times greater affinity than oxygen
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Carbon monoxide CO
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Bright cherry red color of blood is a sign of _
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Monoxide poisoning - complex of heme with CO absorbs light
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Which subunits comprise adult hemoglobin - hemoglobin A
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2 alpha and 2 beta
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Hemoglobin A2 (2%) of adult hemoglobin - which subunits
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2 alpha and 2 delta
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HbF compared to HbA
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HbF has two alpha and two gamma subunits - has higher oxygen affinity, 7 months gestation - 1 month old
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Myoglobin oxygen saturation curve
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Simple hyperbola - Michaelis Menten relationship - simple saturation kinetics
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Hemoglobin oxygen saturation curve
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Rectangular hyperbola - cooperative curve, because it indicates cooperativity of action of individual sub-units of the same Hb molecule in binding oxygen. As one oxygen binds to one Hb sub-unit, it facilitates the binding of subsequent oxygens to other subunits of the same Hb molecule. This behaviour is exactly analogous to that of an allosteric enzyme binding its substrate
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Deoxy form of Hb is _ state, oxy form of Hb is _ stae
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Deoxy - T state
Oxy form - R state |
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Structural differences of oxyhemoglobin vs deoxyhemoglobin
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i) The ferrous atom is closer to the plane of the porphyrin ring in oxyHb. (It is slightly
outside this plane in deoxyHb.) (ii) DeoxyHb possesses several salt linkages (ie charge-charge interactions) which oxyHb does not possess. These linkages appear to stabilize the deoxy form. (iii) The alpha1beta1 dimer is at a different angle to the alpha2beta2 dimer in oxyHb from that in deoxyHb (although the interactions between subunits within the same dimer remain relatively unchanged). |
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Affinity for O2 in hemoglobin with increased or decreased pH
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Increased pH
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Describe Hb as blood buffer
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As Hb binds oxygen it releases hydrogen ions and as it releases oxygen it
binds hydrogen ions (in the tissues). |
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Why does fetal Hb have higher oxygen affinity that adult Hb
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BPG doesnt have its effect on fetal Hb - BPG lowers affinity for oxygen
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2 types of hemoglobinopathies
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Structural (sickle cell) and synthesis (thalassemias)
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glu at position 6 in the beta chain is replaced by val (Glu6Val)
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Sickle cell anemia
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If the person with sickle cell trait is heterozygous would they have the disease
Homozygous? |
NO - carrier
Disease |
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Heterozygous carriers of sickle cell are asymptomatic except
What benefit do they have |
At high altitude
Protected from malaria |
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Confirmation of sickle cell anemia and diagnosis of sickle cell trait is done by _
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Protein electrophoresis
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consequence of a
substitution at position 6 in the beta chain, the glutamic acid being replaced in this case by a lysine (Glu6Lys |
Hb C
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