The Respiratory System III: Physiological Systems and Gas Transport

This flashcard set covers the physiological aspects of the respiratory system, specifically focusing on gas transport, metabolic rates, partial pressure gradients, and the biochemical factors affecting oxygen-haemoglobin dissociation.

Metabolic rate

The rate at which cells use $O_2$ to release energy; at rest, this is approximately $3004.2\,kJ/\text{hour}$ or $4.2\,kJ/\text{hour/kg}$.

Glucose Oxidation Equation

The aerobic process where glucose releases energy: $C_6H_{12}O_6 + 6O_2 \rightarrow 6CO_2 + 6H_2O + 36\text{ ATP molecules}$.

Anaerobic Metabolism

A process occurring during exercise that produces lactic acid and much less ATP than aerobic metabolism ($\text{glucose} \rightarrow \text{pyruvate} + 2\text{ ATP} \rightarrow \text{lactic acid}$).

Partial pressures (P)

Values calculated from the total air pressure and the amount of gas in a mixture; at sea level, total air pressure is $760\,mmHg$.

Pulmonary blood flow gradient

The phenomenon where blood flow through the upright lung is greatest at the base and least at the apex due to gravity and low pulmonary blood pressure ($25/8\,mmHg$).

Haemoglobin (Hb)

A protein in red blood cells essential for the efficient transport of $O_2$ and $CO_2$, consisting of 4 subunits ($2\alpha$ and $2\beta$ in adults) each with an iron-binding site.

Carbon Monoxide (CO)

A poisonous gas that displaces $O_2$ from haemoglobin binding sites.

Co-operative binding

A property of haemoglobin where the binding of each $O_2$ molecule facilitates the binding of additional $O_2$ molecules, resulting in a sigmoidal dissociation curve.

2,3-Bisphosphoglycerate (BPG)

A substance produced in red blood cells via glycolysis that increases $O_2$ dissociation from Hb; its concentration is increased by hormones like $T_3$, growth hormone, and adrenalin.

Bohr shift

The movement of the $O_2$-Hb dissociation curve to the right as pH falls, which causes a greater release of oxygen to active tissues.

Carbonic anhydrase (CA)

The enzyme that catalyzes the equilibrium reaction: $CO_2 + H_2O \rightleftharpoons H_2CO_3 \rightleftharpoons HCO_3^- + H^+$.

Myoglobin

An oxygen-binding protein in skeletal and heart muscle with a very high affinity for $O_2$, used for storing oxygen during anaerobic metabolism due to hypoxia.

Foetal haemoglobin ($2\alpha 2\gamma$)

A form of haemoglobin that has a higher affinity for $O_2$ than adult maternal haemoglobin, allowing oxygen to unload to the fetus via the placenta.

Neonatal jaundice

A condition potentially causing brain damage that arises from the rapid breakdown of foetal haemoglobin after birth as it is replaced by adult haemoglobin.

Carbamino-haemoglobin

The molecule formed when some $CO_2$ binds directly to haemoglobin for transport to the lungs.