Gas Exchange: Form and Function in Plants and Animals

This set of vocabulary flashcards covers the mechanisms of gas exchange, respiratory pigments like hemoglobin and myoglobin, carbon dioxide transport, and various specialized respiratory adaptations in animals.

Gas exchange

The biological process of obtaining $O_2$ for respiration and removing $CO_2$ to prevent a decrease in body pH.

Partial pressure ($P_x$)

The pressure exerted by a specific gas in a gas mixture, which depends on the percentage of the air composed of that gas (e.g., $PO_2$ at sea level is $160\,mmHg$).

Hemoglobin (Hb)

A respiratory pigment protein found in erythrocytes (red blood cells) consisting of 4 subunits, each containing $Fe^+$ that binds with $O_2$.

Anemia

A condition resulting from decreased hemoglobin ($Fe^+$) levels, leading to fatigue.

Cooperative binding (Hb)

The phenomenon where one hemoglobin subunit unloading or taking $O_2$ changes the protein's shape, making it easier for the other subunits to do the same, resulting in an S-shaped dissociation curve.

Fetal Hemoglobin

A version of hemoglobin produced before birth that has a higher affinity for $O_2$ than adult hemoglobin, allowing the fetus to extract oxygen from the mother's blood.

Bohr shift

The shift in the hemoglobin dissociation curve where a decrease in pH (increase in $H^+$) lowers hemoglobin's affinity for $O_2$, causing it to release oxygen more readily in tissues.

2,3-DPG

A phosphate group that increases in humans at high altitudes to lower hemoglobin's $O_2$ affinity, thereby maximizing oxygen delivery to tissues.

Myoglobin

A respiratory pigment found in skeletal and cardiac muscle that stores $O_2$ and has a lower probability of releasing it than hemoglobin at low $PO_2$ (higher $O_2$ affinity).

Hemocyanin

A respiratory pigment found in some invertebrates, such as mollusks and arthropods, that uses copper instead of iron to transport $O_2$.

Bicarbonate Buffer System

The chemical reaction sequence $CO_2 + H_2O \rightarrow H_2CO_3 \rightarrow H^+ + HCO_3^-$ used to transport $CO_2$ and maintain pH balance in the body.

Medulla oblongata and Pons

The breathing control centers in the brain that adjust contraction rates of the rib muscles and diaphragm in response to changes in $CO_2$ and pH levels.

Ventilation

The movement of a respiratory medium (air or water) across a respiratory surface (alveoli or gills).

Tracheal tubes

A system of branched internal tubes in insects that delivers oxygen directly to body cells, independent of the circulatory system.

Spiracles

External openings in an insect's exoskeleton that allow air to enter and exit the tracheal tube system.

Countercurrent exchange

A mechanism in fish gills where blood flows in the opposite direction of water, maintaining a $PO_2$ gradient to maximize the extraction of $O_2$ (up to $80$-$90\%$).

Positive pressure breathing

A ventilation method used by organisms like frogs where air is actively forced or pushed into the lungs.

Negative pressure breathing

A ventilation method used by mammals where the contraction of the diaphragm and rib muscles increases thoracic cavity size, lowering pressure to suck air into the lungs.

Residual volume

The amount of air that remains in the lungs/alveoli after exhalation, which mixes with fresh inhaled air and lowers the overall oxygen extraction efficiency.

Avian Respiration

A highly efficient system of one-way airflow utilizing posterior and anterior air sacs to ensure no residual air remains in the lungs.