Gas laws and gas transfer Flashcards
What is the partial pressure of a gas?
If two separate gases occupy a space, both behave independently and exert their own individual pressure (which is a fraction of the total pressure). The partial pressure refers to the notional pressure of that gas if it occupied the entire volume at room temperature.
What is vapour pressure?
The pressure of a vapour in contact with its liquid or solid form.
[Saturated vapour pressure = partial pressure of water molecules in gas phase, dependent on temperature of system]
What is gas tension in a solution?
Indicates how readily gas will leave a liquid. It is a measure of pressure and therefore does not indicate the physical amount of gas in a liquid.
Measured as a partial pressure of the solute in the solvent in kPa (e.g. oxygen in blood).
What is the content of a gas?
The physical amount of a given gas in a liquid changes with temperature and the gas pressure above it.
Proportional to both its solubility in that liquid and the gas tension at equilibrium.
What is Boyle’s Law?
If a constant amount of gas at a constant temperature is compressed into a smaller volume, the pressure will increase.
So, pressure is inversely proportional to volume.
What is Charles Law?
If a constant amount of gas at a constant pressure is heated, the volume will rise.
So, volume is proportional to temperature.
What is Dalton’s Law?
In a mixture of non-reacting gases, each gas exerts its own partial pressure (which is a fraction of the total pressure). The total pressure exerted is equal to the sum of the partial pressures of the gases.
What is the universal gas law?
Pressure and volume are both proportional to temperature
[So as temperature increases, pressure will increase if volume is constant and volume will need to increase if pressure needs to stay constant]
What factors affect a gas’s ability to dissolve in a liquid?
Solubility (dependent on physical properties of gas or liquid)
Temperature
Pressure
pH of solution
Content of gas (content of gas in a liquid is proportional to its solubility in liquid and the gas tension at equilibrium)
What factors determine a gas’s ability to diffuse across an alveolar membrane?
Gradients of partial pressures
Surface area of alveoli
Resistance (e.g. thickness)
Molecular weight (big molecules diffuse slower)
Solubility (CO2 has a higher solubility than O2)
What is Henry’s Law?
The physical amount of gas dissolving in a solvent is directly proportional to the pressure of the gas at the solvent’s surface
What is the composition of atmospheric air?
pO2 = 21.1 KPa pCO2 = minimal
What is the composition of alveolar air?
pO2 = 13.3 KPa pCO2 = 5.3 KPa
What is the composition of mixed venous blood returning to the lungs?
pO2 = 6.0 KPa pCO2 = 6.5 KPa
[gradient for oxygen to move from alveolar into blood and CO2 into alveolar]
What layers do gases have to pass through in order to diffuse from alveolar into the blood?
- Through gas to alveolar wall
- Epithelial cell of alveolus
- Tissue fluid and connective tissue
- Endothelial cell of capillary
- Plasma
- Red call membrane and cytoplasm
