Topic 1 - Gas Exchange Flashcards
Define diffusion
Net movement of particles (molecules or ions) from area is high conc to low conc
Which way do molecules diffuse
But NET MOVEMENT will be to the area of low conc
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Until particles are evenly distributed throughout liquid or gas
What do most gas exchange surfaces have in common
- Large SA/ volume ratio
- Think (short diffusion pathway)
- Steep conc gradient
What is the gas exchange surface in humans?
Alveolar epithelium in the lungs
Describe gas exchange in lungs
Visa versa with carbon dioxide (breathed out)
4 features of lung that increase rate of gas exchange
- Lots of alveoli (large SA for diffusion)
- Alveolar epithelium and capillary endothelium 1 cell thick
- capillary network gives alveolar good blood supply
- Breathing out ventilates alveoli keeping high conc gradient
Fick’s law describes…
Rate of diffusion
Equation for ficks law
Rate of diffusion =
Area of diffusion surface X difference in conc
______________________
Thickness of diffusion surface
What is the fluid mosaic model?
Describes the arrangement of molecules in a membrane
Why is the bilayer ‘fluid’?
Because phospholipids are constantly moving
What’s the function of cholesterol in the bilayer
Forms bonds to make more rigid
What does the bilayers ‘partial permeability’ mean
Small molecules can pass through the gaps between phospholipids
How do large molecules and ions pass through the bilayer
Channel and carrier proteins
Diffusion through carrier and channel proteins is called..
Facilitated diffusion
process carrier proteins use?
1) large molecule attaches to protein
2) protein changes shape
3) releases protein on opposites side of membrane
