2.1 Gas exchange Flashcards
i) Know the properties of gas exchange surfaces in living organisms (large surface area to volume ratio, thickness of surface, difference in concentration). ii) Understand how the rate of diffusion is dependent on these properties and can be calculated using Fick’s Law of Diffusion. iii) Understand how the structure of the mammalian lung is adapted for rapid gaseous exchange.
What is diffusion?
the net movement of particles from an area of higher concentration to an area of lower concentration
(is a passive process - no energy required)
What are the properties of gas exchange surfaces in living organisms?
- large surface area to volume ratio
- thickness of surface
- difference in concentration
How does surface area to volume ratio of gas exchange surfaces affect gas exchange?
large sa:vol increases rate of gas exchange because there is a larger area for diffusion to occur
How does the thickness of a gas exchange surface affect gas exchange?
thin gas exchange surfaces provide a short diffusion pathway - increases rate of gas exchange
How does the concentration gradient affect gas exchange?
the steeper the concentration gradient, the faster the rate of gas exchange
How does temperature affect rate of diffusion?
increasing temperature increases the kinetic energy of the particles, so they move faster and the rate of gas exchange increases
What is Fick’s law?
the rate of diffusion ∝ (area of diffusion surface x difference in concentration) / thickness of diffusion surface
What happens to the rate of diffusion if SA doubles?
it also doubles
What happens to the rate of diffusion if the difference in concentration doubles?
it also doubles
What happens to the rate of diffusion if the thickness of the gas exchange surface doubles?
it halves
Fick’s law (equation)
………………………(C1-C2)
Rate = P x A x ———–
……………………………T
P = permeability constant
A = surface area
(C1-C2) = diff. in conc.
T = thickness of surface
Where does gas exchange happen in mammals?
gas exchange occurs in the alveoli in the lungs
What do the pulmonary vein and artery do?
P. vein brings deoxygenated blood to lungs
P. artery brings oxygenated blood away from lungs
How does gas exchange occur across the alveolar epithelium?
- air enters the alveolar space
- oxygen from air diffuses out of the alveoli across the alveolar epithelium (a layer of thin flat cells)
- and across the capillary endothelium into the blood
- carbon dioxide diffuses across the capillary endothelium and alveolar epithelium and is then breathed out
How is the mammalian lung adapted for rapid gas exchange?
- lots of alveoli increases SA for increased rate of diffusion
- alveolar epithelium and capillary endothelium only one cell thick (short diffusion pathway
- large supply of capillaries constantly provides deoxygenated blood and removes oxygenated blood, maintaining the conc. gradient
- constant ventilation of lungs ensures air is refreshed in the alveoli, maintaining the conc. gradient
