oxygen dissociation curve (MIDTERM 2)

The function of hemoglobin is to readily bind oxygen mole- cules in the lung, which requires _____ oxygen affinity; to trans- port oxygen; and to efficiently unload oxygen to the tissues, which requires _____ oxygen affinity.

-high -low

Approximately ____ mL of oxygen is bound by each gram of hemoglobin

1.34ml

Myoglobin, present in cardiac and skeletal muscle, is a ____, monomeric, oxygen-binding heme protein

17,000 dalton

Normally, a PO2 of approximately 27 mm Hg results in ____% oxygen saturation of the hemoglobin molecule.

27 mm Hg 50%

Normally, a PO2 of approximately ____ mm Hg results in ___% oxygen saturation of the hemoglobin molecule.

27 mm Hg 50%

Consequently, the RBC count, hemoglobin concentration, and hematocrit of a newborn are higher than adult values (values are on the inside front cover), but they gradually decrease to normal physiologic levels by ___ months of age as the g-b switchjng is completed and most of the Hb F is replaced by Hb A

6 months

The reference interval for arterial oxygen saturation is

96-100%

A shift in the curve due to a change in pH (or hydrogen ion concentration) is termed the

Bohr effect

the primary hemoglobin in new- borns) has a ___ of ___ to ___ mm Hg, which results in a ____ shift of the oxygen dissociation curve and ____ affinity for oxygen relative to that of Hb A.

Hb F (fetal hemoglobin P50 of 19-12 mm Hf Left Increased

If there is a shift of the curve to the right, 50% oxygen saturation of hemoglobin occurs at a PO2 _____ 27 mm Hg.

Higher than

Clinical conditions that produce a shift of the oxygen dissociation curve to the _____ include a lowered body temperature due to external causes; multiple transfusions of stored blood with depleted 2,3-BPG; alkalosis; and the presence of hemoglobin variants with a high affinity for oxygen.

Left

If there is a shift of the curve to the left, 50% oxygen saturation of hemoglobin occurs at a PO2 of _____ 27 mm Hg.

Less than

It binds oxygen with greater affinity than hemoglobin. Its hyperbolic curve indicates that it releases oxygen only at very low partial pressures, which means it is not as effective as hemoglobin in releasing oxygen to the tissues at physiologic oxygen tensions.

Myoglobin

The relationship is described by the ____ which plots the percent oxygen saturation of hemoglobin versus the PO2

Oxygen dissociation curve of hemoglobin

The affinity of hemoglobin for oxygen relates to the partial pressure of oxygen (PO2), often defined in terms of the amount of oxygen needed to saturate 50% of hemoglobin, called the

P50 value.

Myoglobin in the urine produces a ____ result on the urine dipstick test for blood; this must be differentiated from a positive result caused by hemoglobin.

Positive

When the hemoglobin tetramer is fully oxygenated, it assumes a ___

Relaxed or R state

Conditions producing a shift of the curve to the ____ include increased body temperature; acidosis; the presence of hemoglobin variants with a low affinity for oxygen; and increased 2,3-BPG concentration in response to hypoxic conditions, such as high altitude, pulmonary insufficiency, congestive heart failure, and severe anemia

Right

aid in diagnosis of myocardial infarction in patients who have no underlying trauma, rhabdomyolysis, or renal failure.

Serum myoglobin levels

The curve is ____ which indicates low hemoglobin affinity for oxygen at low oxygen tension and high affinity for oxygen at high oxygen tension.

Sigmoidal

In the deoxygenated state, the hemoglobin tetramer assumes a ____ conformation that is stabilized by the binding of 2,3-BPG between the b-globin chains

Tense or T

Con- versely, with the relatively low oxygen tension in the tissues, the affinity of hemoglobin for oxygen is low, and hemoglobin rapidly releases oxygen.

True

Cooperation among hemoglobin subunits contributes to the shape of the curve. Hemoglobin that is completely deoxygenated has little affinity for oxygen.

True

During oxygenation, each of the four heme iron atoms in a hemoglobin molecule can reversibly bind one oxygen molecule

True

Hb F has a disad- vantage in that it delivers oxygen less readily to tissues.

True

In addition to the PO2, shifts of the curve to the left or right occur if there are changes in the pH of the blood

True

Myoglobin is normally excreted by the kidney, but levels may become elevated in renal failure.

True

Once one oxygen molecule binds, the remainder of the hemoglobin molecule quickly becomes fully oxygenated

True

The binding of 2, 3-BPG shifts the oxygen dissociation curve to the right, favoring the release of oxygen.1 In addition, a lower pH and higher PCO2 in the tissues further shifts the curve to the right, favoring the release of oxygen

True

high oxygen tension in the lungs, the affinity of hemoglobin for oxygen is high, and hemoglobin becomes rapidly saturated with oxygen.

True

. The bone marrow in the fetus and newborn compensates by producing more RBCs to ensure adequate oxygenation of the tissues. This response is mediated by

erythropoietin

Myoglobin is released into the plasma when there is damage to the muscle in myocardial infarction, trauma, or severe muscle injury, called

rhabdomyolysis