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BIOLOGY 220 LECTURE #14 - Gas Exchange - 10-28-07

# BIOLOGY 220 LECTURE #14 - Gas Exchange - 10-28-07 - BIOLOGY...

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BIOLOGY 220 LECTURE #14 – GAS EXCHANGE – 10/18/07 GAS EXCHANGE Aerobic respiration o For it to take place in an organism, it requires glucose and oxygen o The process of gas exchange in an organism is simply getting that organism to the appropriate cells so that it can take place Gas exchange o Provide a product o Provide a substrate o Take away a product Gas exchange at the cellular level, o Simple diffusion o Diffusion is taking place at the cellular level so that respiration can occur Putting a gas in a liquid makes the process of diffusion easier Gases can mix – But if you have a liquid, diffusion can happen a lot easier Simple diffusion isn’t enough to drive the process of respiration, so we use gas exchange to help that process along GAS EXCHANGE: FICK’S LAW – (3) Diffusion happens as a result of random motion – they want to get away from their fellow molecules as much as possible o Can be put in mathematical terms Fick’s Law of Diffusion – All about the rate of diffusion D The diffusion constant is different for every type of molecule and every type of situation o Takes into consideration that molecules vibrate at different temperatures o A larger molecule will move differently than a smaller molecule o This would be different for sucrose at room temperature versus in the freezer A Area across which diffusion takes place o Can diffusion take place across a large area or do we have a really small area o Surface area

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P1 – P2 (replace with “c”) – Pressure concentration differences between two systems o A way of saying concentration is really high over here, concentration is really low over there – that difference is going to be larger, so diffusion will happen faster o We use the term “pressure,” because it’s a better descriptor in terms of how gases are going to move – we use it synonymously with “concentration” Solutes move from low concentration to high concentration Air, oxygen, carbon dioxide Gases will move from area of high concentration (high pressure) to area of low concentration (low pressure) d The difference between system A and system B o Physical linear distance between the two systems o Generally, diffusion is only really effective is “d” is tiny (less than a mm) o This (Fick’s Law) will tell you if diffusion is going to take place quickly or slowly GAS EXCHANGE: FICK’S LAW - (4) Maximize the rate of diffusion: o Increasing surface area Huge surface area that can be bombarded with molecules, then diffusion is going to happen at a faster rate – more likely that a molecule will find a direct path into the new system o Minimize the diffusion distance Make “d” small o Increasing the concentration gradient All animals have a respiratory/gas exchange system that attempts to do at least one of the above items that maximize the rate of diffusion (and hence gas exchange with the environment – because gas exchange depends on the environment)
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