Biochemd Ch.7

Front 1

Hemoglobin

Back 1

contained in red blood cells (RBC) and serves as the oxygen carrier in blood

Front 2

Myoglobin

Back 2

in muscle and serves as a reserve carrier of oxygen and also facilitates the movement of oxygen within muscle

Front 3

heme group

Back 3

protoporphyrin (four pyrrole groups) and an iron atom
gives ability of both myoglobin and hemoglobin to bind oxygen

Front 4

myoglobin structure for heme

Back 4

group is located near the surface of the myoglobin molecule in a crevice which, with the exception of the two histidine residues mentioned above, provides a nonpolar environment. The plane of the heme lies between the two histidine residues being bound to the iron atom at its fifth coordination position. The second histidine residue is positioned on the other side of the heme plane but is not bound directly to the sixth coordinate position because this constitutes the binding site for oxygen. Upon oxygenation, the iron atom descends into the heme plane and the oxygen bound to the myoglobin is stabilized by hydrogen bonding to the imidazole ring of one of the histidines.

Front 5

hemoglobin structure

Back 5

four polypeptide chains which are held together by noncovalent interactions. Each chain contains one heme group and, consequently, there are four binding sites for oxygen. Chains form nonpolar regions around binding site.

Front 6

sigmoidal oxygen binding curve for hemoglobin indicates that oxygen binding occurs in a ____ fashion

Back 6

cooperative

Front 7

myoglobin has a _____ affinity for oxygen than hemoglobin

Back 7

higher

Front 8

higher the pH (the lower the H+ concentration) at a given partial pressure of oxygen, the _____ the percent saturation with oxygen

Back 8

greater

Front 9

Bohr Effect

Back 9

strong effect of pH on the oxygen-hemoglobin equilibrium

Front 10

hemoglobin transportation in lungs

Back 10

higher partial pressure of O2 and highish pH = oxygenation and release of H+ and CO2
HCO-3 + H+ = CO2 and H2O
CO2 is excreted

Front 11

oxygenated hemoglobin in tissues

Back 11

low O2 tension and low pH = O2 release

Front 12

transport of CO2 from tissues

Back 12

89% carried as HCO-3 in rbc
6% bound to alpha-amino groups of hemoglobin as carbamate
5% carried as dissolved CO2 in plasma

Front 13

hydrogen ion transportation

Back 13

Hydrogen ion resulting from HCO-3 production from CO2 and H2O and from carbamate formation will bind to the deoxyhemoglobin molecule.

Front 14

2,3-bisphosphoglycerate (BPG)

Back 14

a molecule that helps regulate oxygen binding to hemoglobin. BPG occurs in red blood cells in equimolar amounts with hemoglobin and markedly reduces hemoglobin's affinity for oxygen.

Front 15

sickle-cell anemia

Back 15

red blood cells tend to assume a crescent or sickle shape at low oxygen tensions

The alpha chains of the two forms are identical, but the glutamic acid residue (hydrophilic) at position six of the beta chain is replaced with valine (hydrophobic) in hemoglobin S. The two valines at position 1 and 6 form a hydrophobic association which results in the deoxyhemoglobin S molecule assuming a conformation that stacks in long tubular fibers causing the shape of the red cell to become distorted.