Eric NiederhofferSIU-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 transportcarbonic anhydrase, anion exchanger, carbamate formation, Bohr effect

• NO processing and transportglutathione

• O2 processing and transporthemoglobin/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 VenousCarbamino 5 30HCO3

- 87 60CO2 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?