Respiratory Physiology: Transport of Gases

Flashcards covering the physiological mechanisms of oxygen and carbon dioxide transport, hemoglobin properties, and clinical states affecting gas exchange.

O2 content

The actual amount of $O_2$ per volume of blood, calculated as: $(1.34 \times \text{Hb concentration} \times SO_2) + (0.003 \times PO_2)$

1.34

The maximum volume of $O_2$ (in $mL$) that $1$ gram of fully saturated Hemoglobin ($Hb$) can bind.

0.003

The solubility coefficient of $O_2$ in plasma, expressed as $mL$ of $O_2/100\text{ mL}$ of blood per $mm\text{ Hg}$.

Hemoglobin-bound O2

The portion of molecular oxygen representing $98\%$ of total transport, found within the Red Blood Cells ($RBCs$).

Dissolved O2

The portion of molecular oxygen representing $2\%$ of total transport, found within the plasma.

Methemoglobin

A form of Hemoglobin where iron is in the Ferric ($Fe^{3+}$) state; it cannot bind to $O_2$, causes a left shift in the ODC, and results in chocolate-colored blood.

Fetal Hb (HbF)

Hemoglobin composed of $\alpha_2\gamma_2$ polypeptide chains that has a higher affinity for $O_2$ than adult hemoglobin due to poor binding of $2,3\text{-BPG}$.

Positive cooperativity

The property of the tetrameric Hemoglobin molecule where binding one $O_2$ molecule increases the affinity for subsequent $O_2$ molecules, creating a sigmoid-shaped ODC.

Tense (T) configuration

The configuration of globin units in deoxygenated Hemoglobin which possesses a low affinity for $O_2$.

Relaxed (R) configuration

The configuration acquired by globin units upon oxygenation which possesses an increased affinity for $O_2$.

P50

The partial pressure of oxygen ($PO_2$) at which hemoglobin is half saturated ($50\%$) with $O_2$, normally valued at $25-27\text{ mmHg}$.

Myoglobin

A monomeric molecule that lacks positive cooperativity, resulting in a hyperbolic ODC and a higher affinity for $O_2$ than Hemoglobin.

CADET (Right Shift Factors)

An acronym for factors that shift the ODC to the right (decreasing affinity/increasing unloading): $\uparrow PCO_2$, $\uparrow\text{Acid (H}^+\text{)}$, $\uparrow 2,3\text{-BPG}$, $\uparrow\text{Exercise}$, and $\uparrow\text{Temperature}$.

Bohr Effect

A right shift of the Oxygen Dissociation Curve in response to increased blood $CO_2$ and $H^+$ ions, promoting $O_2$ unloading at tissues.

2,3-Bisphosphoglycerate (2,3-BPG)

A byproduct of glycolysis in RBCs that binds to the $\beta\text{-chain}$ of deoxy-$Hb$, decreasing oxygen affinity to promote unloading.

Carboxyhemoglobin

A complex formed when Carbon Monoxide ($CO$) binds competitively to Hemoglobin with a greater than $200\text{ times}$ affinity compared to oxygen.

Cyanide toxicity

A condition where $PaO_2$ and the ODC are normal, but tissues cannot use oxygen due to ineffective oxidative phosphorylation; characterized by cherry-red skin and bitter-almond breath odor.

Haldane effect

The phenomenon in the lungs where the binding of $O_2$ to Hemoglobin displaces $CO_2$ from the blood to be exhaled.

Chloride shift

The movement of chloride into red cells in venous blood (causing cell swelling) and out of red cells in arterial blood (causing cell shrinking).

Carbaminohemoglobin (HbCO2)

A form of $CO_2$ transport where $CO_2$ is bound to Hemoglobin at the N-terminus of globin, accounting for $20-25\%$ of transport.