Eric Niederhoffer
SIU-SOM
How are CO2, NO, and O2 processed and transported?
A 40-year-old man complains of progressive exertional shortness of breath
A 4-year-old African boy is brought in by his adoptive parents who say that he has pain in his limbs and
does not want to walk
How is heme synthesized?
Small Molecule Processing and Transport
• CO2 processing and transport
carbonic anhydrase, anion exchanger, carbamate formation, Bohr effect
• NO processing and transportglutathione
• O2 processing and transport
hemoglobin/myoglobin structure, allostery, cooperativity
• Heme synthesispathway, disorders
CO2 Processing and Transport
CO2 CO2
H2OCA
H2CO3
H+Hb
Hb(O2)4
O2HCO3-HCO3
- O2
HbNH2
HbNH-CO2-H++ + +
+ +
from tissues
to tissuesplasma
Cl- Cl-AE1
CO2 CO2
H2OCA
H2CO3
H+Hb
Hb(O2)4
O2HCO3-HCO3
- O2
HbNH2
HbNH-CO2-H++ + +
+ +
to air
from airplasma
Cl- Cl-AE1
Percent Distribution of CO2
Species Arterial Venous
Carbamino 5 30
HCO3- 87 60
CO2 dissolved 8 10
NO Processing and Transport
http://www.comprehensivephysiology.com/WileyCDA/CompPhysArticle/refId-c090009.html
Hemoglobin Structure Changes
http://www.mfi.ku.dk/PPaulev/chapter8/images/8-3.jpg
Factors Affecting Binding of O2
Depends on pH ([H+]), CO2, BPG, Temp
Factors Affecting Binding of O2Adaptation
Figures from http://www.wiley.com/college/voet/047119350X/image_gallery/
ch10/index.html
Heme Synthesismit
SCoA + Gly
5-Aminolevulinic acid synthase
5ALAPBG
Porphobilinogen synthase
PBG deaminase
Hydroxymethylbilane
Uroporphyrinogen III synthase
UPGIII
UPGIII decarboxylase
CPGIIICoproporphyrinogen oxidase
PPGIX
PPIX
Protoporphyrinogen oxidase
Ferrochelatase
Heme
Pb
Pb
Review Questions• How are CO2 and NO processed and transported?
• How are myoglobin and hemoglobin similar and
different?
• What portion of hemoglobin is involved in small
molecule transport?
• What allosteric effectors bind hemoglobin?
• How do allosteric effectors produce left and right
shifts of the hemoglobin-O2 binding curves?
• How is heme synthesized?
• How is heme synthesis regulated?
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