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24 Cards in this Set

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At low oxygen tension, will there be higher oxygen affinity in hemoglobin or myoglobin
Myoglobin
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
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
75% of hemoglobin structure is _
Alpha helix
Heme group is _
Porphyrin ring (protoporphyrin IX)
What gives color to the blood?
Absorption of light by heme
Can bind to hemoglobin with 2000 times greater affinity than oxygen
Carbon monoxide CO
Bright cherry red color of blood is a sign of _
Monoxide poisoning - complex of heme with CO absorbs light
Which subunits comprise adult hemoglobin - hemoglobin A
2 alpha and 2 beta
Hemoglobin A2 (2%) of adult hemoglobin - which subunits
2 alpha and 2 delta
HbF compared to HbA
HbF has two alpha and two gamma subunits - has higher oxygen affinity, 7 months gestation - 1 month old
Myoglobin oxygen saturation curve
Simple hyperbola - Michaelis Menten relationship - simple saturation kinetics
Hemoglobin oxygen saturation curve
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
Deoxy form of Hb is _ state, oxy form of Hb is _ stae
Deoxy - T state

Oxy form - R state
Structural differences of oxyhemoglobin vs deoxyhemoglobin
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).
Affinity for O2 in hemoglobin with increased or decreased pH
Increased pH
Describe Hb as blood buffer
As Hb binds oxygen it releases hydrogen ions and as it releases oxygen it
binds hydrogen ions (in the tissues).
Why does fetal Hb have higher oxygen affinity that adult Hb
BPG doesnt have its effect on fetal Hb - BPG lowers affinity for oxygen
2 types of hemoglobinopathies
Structural (sickle cell) and synthesis (thalassemias)
glu at position 6 in the beta chain is replaced by val (Glu6Val)
Sickle cell anemia
If the person with sickle cell trait is heterozygous would they have the disease

Homozygous?
NO - carrier

Disease
Heterozygous carriers of sickle cell are asymptomatic except

What benefit do they have
At high altitude

Protected from malaria
Confirmation of sickle cell anemia and diagnosis of sickle cell trait is done by _
Protein electrophoresis
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