Oxygen Transport and the Oxygen-Hemoglobin Dissociation Curve

A complete set of vocabulary flashcards covering oxygen transport mechanisms, hemoglobin loading and unloading, the oxygen-hemoglobin dissociation curve, and affinity-driven curve shifts.

Dissolved Oxygen Transport

The method of oxygen transport where oxygen travels in gas form dissolved within blood plasma, accounting for only $1.5\%$ of all transported oxygen due to its poor solubility in water.

Hemoglobin

The iron-containing protein located inside erythrocytes that contains $4$ heme groups and transports the vast majority of oxygen in the blood, carrying up to $4$ molecules of $O_2$.

Fully Saturated Hemoglobin

A hemoglobin molecule that has all $4$ of its heme binding sites occupied by oxygen molecules.

Partially Saturated Hemoglobin

A hemoglobin molecule that has only $1$ to $3$ molecules of oxygen bound to its heme groups.

Oxygen Loading

The physiological reaction occurring in the pulmonary capillaries of the lungs where oxygen from alveolar air binds to hemoglobin within erythrocytes.

Oxygen Unloading

The physiological reaction occurring in the systemic capillaries where oxygen detaches from hemoglobin, leaves the erythrocytes, and diffuses into tissue cells.

Oxygen-Hemoglobin Dissociation Curve

A graphical representation demonstrating the relationship between the percent saturation of hemoglobin on the y-axis and the partial pressure of oxygen ($P_{O_2}$ in $\text{mm\,Hg}$) in the blood post gas exchange on the x-axis.

Resting Tissue Hemoglobin Saturation Point

The intermediate point on the dissociation curve post gas exchange where blood $P_{O_2}$ drops to systemic capillary levels and hemoglobin saturation decreases by approximately $25\%$, corresponding to the loss of $1$ of $4$ bound oxygen molecules per hemoglobin.

Metabolically Active Tissue Saturation Point

The point on the lower portion of the dissociation curve where extensive tissue gas exchange reduces blood $P_{O_2}$ further, dropping hemoglobin saturation by an additional $50\%$ ($75\%$ total decrease) so that hemoglobin retains only $1$ of its $4$ original oxygen molecules.

Sigmoidal Curve (S-shape)

The characteristic S-shaped curve of oxygen-hemoglobin dissociation that arises because hemoglobin's affinity for oxygen changes based on its current level of saturation.

Plateau Region of Hemoglobin Saturation

The flat upper portion of the dissociation curve occurring across higher blood $P_{O_2}$ values ($80$ to $100\,\text{mm\,Hg}$) where fully saturated hemoglobin exhibits high affinity and holds tightly to oxygen, preventing premature unloading in systemic arteries.

Steep Section of the Dissociation Curve

The narrow range of lower $P_{O_2}$ values found in systemic capillaries where partially saturated hemoglobin has a lower affinity and unloads bound oxygen rapidly to meet tissue demands.

Factors Altering Hemoglobin Affinity

Physiological variables capable of shifting hemoglobin's affinity for oxygen, specifically temperature, blood pH, partial pressure of carbon dioxide ($P_{CO_2}$), and the compound BPG.

Right Shift of the Dissociation Curve

A displacement of the curve reflecting a decrease in hemoglobin affinity for oxygen, indicating that hemoglobin holds oxygen more loosely, thereby favoring more unloading at higher partial pressures of oxygen.

Left Shift of the Dissociation Curve

A displacement of the curve reflecting an increase in hemoglobin affinity for oxygen, indicating that hemoglobin holds oxygen more tightly, thereby resulting in less unloading and requiring lower partial pressures of oxygen to release oxygen.

Affinity-Induced Curve Shifts

The visual shifting of the oxygen-hemoglobin dissociation curve where decreased affinity shifts the curve to the right (more unloading) and increased affinity shifts the curve to the left (less unloading).