Term
| Erythrocyte(RBC) general info |
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Definition
No nuclei, no protein synthesis, no mitochondria, Oxidizing environment
Heme: 4 pyrole rings joind by methenyl
bridges
Hemes double bonds absorb @ 440-450nm
Central ferrous(Fe2+) forms bonds with
proximal histidine on a-helix of each
globin chain
In oxygenation a bond forms with O on distal histidine side. |
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Term
| Blood color, oxygen state |
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Definition
Oxygenated: red
Deoxygenated: blue
Carboxy-Hb: cherry red |
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Term
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Definition
Mb:
steep hyperbolic curve
Very high O2 affinity
Loading-unloading driven only by pO2
Hb:
Sigmoid curve
Inter-subunit cooperation (un)loading |
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Term
| Changes in Hemoglobin. Disease |
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Definition
HbS: Glu -> Val on B chain
HbC: Glu -> Lys on B chain
HbA1c: non enzymatically glycosylated Hb
in diabetes mellitus |
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Term
| Organization of globin genes |
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Definition
Chromosone 16:
2 genes for a-globin, 1 for Zeta
Chromosome 11:
1 gene for B-globin, 1 for epislon
2 for gamma |
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Term
| Methemoglobin / Metmyoglobin |
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Definition
Oxidation of Fe+2 to Fe+3 yields
non-functional Hb and Mb
RBC stops oxidation by ascorbate(Vit c)
Vit C reacts with oxidants before
they react with Fe
Congenital methemoglobinemia(HbM):
proximal histidine replaced by
tyrosine.(pKa 10)
No proper binding of Fe+2 |
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Term
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Definition
reduces methemoglobin to normal.
NADH = reducing agent/coenzyme |
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Term
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Definition
Binds 200x more tightly than O2 to heme
site. Also locks bound O2 to heme.
1st reaction in breakdown of heme yields CO and Fe3+
1% of carboxyhemoglobin is upper tolerance
CO poisoning: bright cherry-red blood.
Raise partial pO2 to treat. (smokers) |
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Term
| Relaxed and Tensed states of Hb |
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Definition
Unoxygenated: tense. found in tissue
Oxygenated: relaxed found in lungs
Relaxed binds O 300x more than tense
O2 binding pulls on proixmal histidine. Breaks some salt and H bonds.
Valine also pushed due to angular change of central axis |
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Term
| Cooperative binding of O2 |
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Definition
2,3 BPG helps release O2 at tissues.
Binds histydl groups on B chains.
BPG rises in hypoxia and high altitude.
No effect on O2 uptake but promotes
unloading in tissues.
Embryonic and Fetal HB have higher O2 binding affinities then HbA |
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Term
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Definition
Acid lowers affinity of O2 to hemoglobin.
In metabolizing tissues:
Co2 + H20 -> HCO3- + H+.
In diabetes mellitus, patient can be
keto-acidotic. pH < 7.0 = lethal
H+ promotes unloading of O2 |
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Term
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Definition
CO2 binds to terminal NH2 groups of
of a and B chains of hemoglobin.
(Non enzymatically)
CO2 reduces Hb's affinity for oxygen.
(unloading) |
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Term
| Basic Vs acidic Amino Acids |
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Definition
Basic: Histidine, lysine, arginine
Acidic: Aspartic Acid, Glutamic Acid |
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Term
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Definition
pH = pKa + log [A-] / [HA]
When pH = pKa acid is 50% pronated and
50% unpronated. (weak acid at its
strongest buffering power) |
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Term
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Definition
Carboxyl pK = 1.8
R-(imidazole) pk = 6.0
a-amino gorup pK = 9.2
Isoelectric = 7.6
Histidine allows body to maintain
acid/base ratio over range of body
temperatures |
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Term
| When is an amino acids two ionizable groups most likely to be ionized? |
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Definition
| When mediums pH is most differetn from the pKa value of each group |
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Term
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Definition
pK = 6.1 for HCO3-
pH = 6.1 + log [HCO3-] / [CO2]
Normal ratio = 20.
Below = acidoses. above = alkalatoic
Normal plasma pH is 7.4 |
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Term
| Chloride-Bicarbonate Exhanger |
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Definition
Antiport. No ATP required.
Increases permeability by more than 10^6 |
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Term
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Definition
CO2 + H20 <-> H2CO3
(carbonic anhydrase Zn++)
H2CO3 <-> H+ + HCO3- |
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